diff --git a/.github/workflows/buildci.yml b/.github/workflows/buildci.yml
index ddf8cde..5a58cc6 100644
--- a/.github/workflows/buildci.yml
+++ b/.github/workflows/buildci.yml
@@ -11,6 +11,7 @@ on:
 jobs:
   build:
     runs-on: ${{ matrix.os }}
+    timeout-minutes: 10
 
     strategy:
       # Set fail-fast to false to ensure that feedback is delivered for all matrix combinations. Consider changing this to true when your workflow is stable.
@@ -56,6 +57,7 @@ jobs:
 
   format:
     runs-on: ubuntu-latest
+    timeout-minutes: 5
 
     steps:
       - uses: actions/checkout@v4
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 01f2380..8dac12a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -73,6 +73,8 @@ set_property(TEST leak_with_global.vpy PROPERTY WILL_FAIL true)
 set_property(TEST invalid_read.vpy PROPERTY WILL_FAIL true)
 set_property(TEST invalid_shared_region.vpy PROPERTY WILL_FAIL true)
 set_property(TEST invalid_write.vpy PROPERTY WILL_FAIL true)
-set_property(TEST fail_cross_region_reg.vpy PROPERTY WILL_FAIL true)
+set_property(TEST invalid_child_region.vpy PROPERTY WILL_FAIL true)
+set_property(TEST invalid_not_bridge.vpy PROPERTY WILL_FAIL true)
 set_property(TEST region_bad_1.vpy PROPERTY WILL_FAIL true)
 set_property(TEST region_bad_2.vpy PROPERTY WILL_FAIL true)
+set_property(TEST fail_cross_region_ref.vpy PROPERTY WILL_FAIL true)
diff --git a/docs/builtin.md b/docs/builtin.md
index 2dfdce6..03395c5 100644
--- a/docs/builtin.md
+++ b/docs/builtin.md
@@ -12,7 +12,7 @@ Aborts the interpreter process. It's intended to indicate that an execution bran
 
 ## Constructors
 
-#### `region()`
+#### `Region()`
 
 Creates a new region object.
 
@@ -74,7 +74,15 @@ This explicitly shows the "Cown region" in the generated diagrams.
 
 #### `mermaid_hide_cown_region()`
 
-This hides the "Cown region" and cown prototype in diagram. (This is the default)
+This hides the "Cown region" and cown prototype in diagram. (Default)
+
+#### `mermaid_show_immutable_region()`
+
+This explicitly shows the "Immutable region" in the generated diagrams
+
+#### `mermaid_hide_immutable_region()`
+
+This hides the "Immutable region" in diagram. (Default)
 
 #### `mermaid_show_functions()`
 
@@ -82,4 +90,4 @@ Shows user defined functions in the diagram.
 
 #### `mermaid_hide_functions()`
 
-Hides user defined functions in the diagram. (This is the default)
+Hides user defined functions in the diagram. (Default)
diff --git a/src/rt/core.h b/src/rt/core.h
index 5828145..e8cb353 100644
--- a/src/rt/core.h
+++ b/src/rt/core.h
@@ -196,19 +196,24 @@ namespace rt::core
   class CownObject : public objects::DynObject
   {
   public:
-    CownObject(objects::DynObject* region)
+    CownObject(objects::DynObject* bridge)
     : objects::DynObject(cownPrototypeObject(), objects::cown_region)
     {
-      // FIXME: Add once regions are reified
-      // assert(
-      //   region->get_prototype() == regionPrototype() &&
-      //   "Cowns can only store regions");
-      //
-      // FIXME: Also check that the region has a LRC == 1, with 1
-      // being the reference passed into this constructor
+      auto region = objects::get_region(bridge);
+      if (region->bridge != bridge)
+      {
+        std::stringstream ss;
+        ss << bridge << " is not the bridge object of the region";
+        ui::error(ss.str(), bridge);
+      }
+
+      if (region->local_reference_count > 1)
+      {
+        ui::error("The given region has a LRC > 1", bridge);
+      }
 
       // this->set would fail, since this is a cown
-      this->fields["value"] = region;
+      this->fields["value"] = bridge;
     }
 
     std::string get_name() override
@@ -233,7 +238,7 @@ namespace rt::core
   {
     static std::set<objects::DynObject*>* globals =
       new std::set<objects::DynObject*>{
-        objects::regionObjectPrototypeObject(),
+        objects::regionPrototypeObject(),
         framePrototypeObject(),
         funcPrototypeObject(),
         bytecodeFuncPrototypeObject(),
diff --git a/src/rt/core/builtin.cc b/src/rt/core/builtin.cc
index 3656029..af0e478 100644
--- a/src/rt/core/builtin.cc
+++ b/src/rt/core/builtin.cc
@@ -124,6 +124,19 @@ namespace rt::core
       return std::nullopt;
     });
 
+    add_builtin(
+      "mermaid_show_immutable_region", [mermaid](auto, auto, auto args) {
+        assert(args == 0);
+        mermaid->draw_immutable_region = true;
+        return std::nullopt;
+      });
+    add_builtin(
+      "mermaid_hide_immutable_region", [mermaid](auto, auto, auto args) {
+        assert(args == 0);
+        mermaid->draw_immutable_region = false;
+        return std::nullopt;
+      });
+
     add_builtin("mermaid_show_functions", [mermaid](auto, auto, auto args) {
       assert(args == 0);
       mermaid->show_functions();
diff --git a/src/rt/objects/region.cc b/src/rt/objects/region.cc
index 4958010..68bee31 100644
--- a/src/rt/objects/region.cc
+++ b/src/rt/objects/region.cc
@@ -52,7 +52,7 @@ namespace rt::objects
         return false;
       }
 
-      if (obj->get_prototype() != objects::regionObjectPrototypeObject())
+      if (obj->get_prototype() != objects::regionPrototypeObject())
       {
         ui::error("Cannot add interior region object to another region");
       }
@@ -133,7 +133,7 @@ namespace rt::objects
       return;
     }
 
-    if (target->get_prototype() != objects::regionObjectPrototypeObject())
+    if (target->get_prototype() != objects::regionPrototypeObject())
     {
       ui::error("Cannot add interior region object to another region");
     }
@@ -251,4 +251,19 @@ namespace rt::objects
     return obj;
   }
 
+  void Region::action(Region* r)
+  {
+    if ((r->local_reference_count == 0) && (r->parent == nullptr))
+    {
+      // TODO, this can be hooked to perform delayed operations like send.
+      //  Needs to check for sub_region_reference_count for send, but not
+      //  deallocate.
+
+      if (r != get_local_region() && r != cown_region)
+      {
+        to_collect.push_back(r);
+        std::cout << "Collecting region: " << r << std::endl;
+      }
+    }
+  }
 }
diff --git a/src/rt/objects/region.h b/src/rt/objects/region.h
index 9344127..7a228e5 100644
--- a/src/rt/objects/region.h
+++ b/src/rt/objects/region.h
@@ -55,18 +55,7 @@ namespace rt::objects
       return local_reference_count + sub_region_reference_count;
     }
 
-    static void action(Region* r)
-    {
-      if ((r->local_reference_count == 0) && (r->parent == nullptr))
-      {
-        // TODO, this can be hooked to perform delayed operations like send.
-        //  Needs to check for sub_region_reference_count for send, but not
-        //  deallocate.
-
-        to_collect.push_back(r);
-        std::cout << "Collecting region: " << r << std::endl;
-      }
-    }
+    static void action(Region*);
 
     static void dec_lrc(Region* r)
     {
@@ -117,9 +106,9 @@ namespace rt::objects
       // Check if already parented to another region.
       if (r->parent != nullptr)
       {
-        // FIXME: Highlight, once regions have been reified
         ui::error(
-          "Region already has a parent: Creating region DAG not supported!");
+          "Region already has a parent: Creating region DAG not supported!",
+          r->bridge);
       }
 
       // Prevent creating a cycle
@@ -129,7 +118,7 @@ namespace rt::objects
         if (ancestors == r)
         {
           // FIXME: Highlight, once regions have been reified
-          ui::error("Cycle created in region hierarchy");
+          ui::error("Cycle created in region hierarchy", r->bridge);
         }
         ancestors = ancestors->parent;
       }
diff --git a/src/rt/objects/region_object.h b/src/rt/objects/region_object.h
index 4847f6a..595a81a 100644
--- a/src/rt/objects/region_object.h
+++ b/src/rt/objects/region_object.h
@@ -1,11 +1,12 @@
 #pragma once
 
 #include "prototype_object.h"
+#include "region.h"
 
 namespace rt::objects
 {
   // The prototype object for region entry point objects
-  inline PrototypeObject* regionObjectPrototypeObject()
+  inline PrototypeObject* regionPrototypeObject()
   {
     static PrototypeObject* proto = new PrototypeObject("RegionObject");
     return proto;
@@ -14,8 +15,17 @@ namespace rt::objects
   class RegionObject : public DynObject
   {
   public:
-    RegionObject(Region* region)
-    : DynObject(regionObjectPrototypeObject(), region)
-    {}
+    RegionObject(Region* region) : DynObject(regionPrototypeObject(), region) {}
+
+    std::string get_name() override
+    {
+      auto region = get_region(this);
+
+      std::stringstream stream;
+      stream << this << std::endl;
+      stream << "lrc=" << region->local_reference_count << std::endl;
+      stream << "sbrc=" << region->sub_region_reference_count;
+      return stream.str();
+    }
   };
-}
\ No newline at end of file
+}
diff --git a/src/rt/rt.cc b/src/rt/rt.cc
index ac48528..b04419d 100644
--- a/src/rt/rt.cc
+++ b/src/rt/rt.cc
@@ -92,7 +92,7 @@ namespace rt
   {
     // TODO Add some checking.  This is need to lookup the correct function in
     // the prototype chain.
-    if (key->get_prototype() != core::stringPrototypeObject())
+    if (key && key->get_prototype() != core::stringPrototypeObject())
     {
       ui::error("Key must be a string.", key);
     }
diff --git a/src/rt/ui.h b/src/rt/ui.h
index 816e02e..163336e 100644
--- a/src/rt/ui.h
+++ b/src/rt/ui.h
@@ -57,8 +57,10 @@ namespace rt::ui
     std::set<rt::objects::DynObject*> taint;
     /// Indicates if the cown region show be explicitly drawn
     bool draw_cown_region;
+    bool draw_immutable_region;
     /// Indicates if local functions should be visible
     bool draw_funcs;
+    bool highlight_unreachable = true;
 
     std::vector<objects::DynObject*> error_objects;
     std::vector<objects::Edge> error_edges;
diff --git a/src/rt/ui/mermaid.cc b/src/rt/ui/mermaid.cc
index 9614c22..0063d0d 100644
--- a/src/rt/ui/mermaid.cc
+++ b/src/rt/ui/mermaid.cc
@@ -17,13 +17,19 @@ namespace rt::ui
   const char* UNREACHABLE_NODE_COLOR = "red";
   const char* ERROR_NODE_COLOR = "red";
 
-  const char* IMMUTABLE_REGION_COLOR = "#32445d";
+  const char* IMMUTABLE_NODE_COLOR = "#243042";
+  const char* IMMUTABLE_REGION_COLOR = "#485464";
   const char* IMMUTABLE_EDGE_COLOR = "#94f7ff";
 
+  const char* REGION_COLORS[] = {
+    "#666", "#555", "#444", "#333", "#222", "#111"};
+
   const char* LOCAL_REGION_ID = "LocalReg";
   const char* IMM_REGION_ID = "ImmReg";
   const char* COWN_REGION_ID = "CownReg";
 
+  const char* FONT_SIZE = "16px";
+
   void replace(std::string& text, std::string from, std::string replace)
   {
     size_t pos = 0;
@@ -44,6 +50,7 @@ namespace rt::ui
     replace(text, "<", "#60;");
     replace(text, ">", "#62;");
     replace(text, "\"", "#34;");
+    replace(text, "\n", "<br/>");
     return text;
   }
 
@@ -60,6 +67,13 @@ namespace rt::ui
     return os;
   }
 
+  struct RegionInfo
+  {
+    std::vector<size_t> nodes;
+    std::vector<objects::Region*> regions;
+    bool drawn;
+  };
+
   class MermaidDiagram
   {
     MermaidUI* info;
@@ -70,14 +84,14 @@ namespace rt::ui
 
     // Give a nice id to each object.
     std::map<objects::DynObject*, NodeInfo> nodes;
-    std::map<objects::Region*, std::vector<std::size_t>> region_strings;
+    std::map<objects::Region*, RegionInfo> regions;
 
   public:
     MermaidDiagram(MermaidUI* info_) : info(info_), out(info->out)
     {
       // Add nullptr
       nodes[nullptr] = {0};
-      region_strings[rt::objects::immutable_region].push_back(0);
+      regions[objects::immutable_region].nodes.push_back(0);
     }
 
     void color_edge(size_t edge_id, const char* color)
@@ -90,26 +104,55 @@ namespace rt::ui
     {
       // Header
       out << "```mermaid" << std::endl;
+      out << "%%{init: {'themeVariables': { 'fontSize': '" << FONT_SIZE
+          << "' }}}%%";
       out << "graph TD" << std::endl;
+      out << "  id0(None):::immutable" << std::endl;
 
       draw_nodes(roots);
       draw_regions();
       draw_taint();
       draw_error();
-      draw_info();
 
-      out << "style " << IMM_REGION_ID << " fill:" << IMMUTABLE_REGION_COLOR
-          << std::endl;
       out << "classDef unreachable stroke-width:2px,stroke:"
           << UNREACHABLE_NODE_COLOR << std::endl;
       out << "classDef error stroke-width:4px,stroke:" << ERROR_NODE_COLOR
           << std::endl;
       out << "classDef tainted fill:" << TAINT_NODE_COLOR << std::endl;
+      out << "classDef immutable fill:" << IMMUTABLE_NODE_COLOR << std::endl;
       // Footer (end of mermaid graph)
       out << "```" << std::endl;
     }
 
   private:
+    std::pair<const char*, const char*> get_node_style(objects::DynObject* obj)
+    {
+      if (obj->get_prototype() == core::cownPrototypeObject())
+      {
+        return {"[[", "]]"};
+      }
+
+      if (obj->get_prototype() == objects::regionPrototypeObject())
+      {
+        return {"[\\", "/]"};
+      }
+
+      if (obj->is_immutable())
+      {
+        // Make sure to also update the None node, when editing these
+        return {"(", ")"};
+      }
+
+      return {"[", "]"};
+    }
+
+    bool is_borrow_edge(objects::Edge e)
+    {
+      return e.src != nullptr && e.target != nullptr &&
+        objects::get_region(e.src) != objects::get_region(e.target) &&
+        objects::get_region(e.src) == objects::get_local_region();
+    }
+
     /// @brief Draws the target node and the edge from the source to the target.
     NodeInfo* draw_edge(objects::Edge e, bool reachable)
     {
@@ -123,7 +166,7 @@ namespace rt::ui
       {
         auto src_node = &nodes[src];
         out << "  " << *src_node;
-        out << ((src_node->is_opaque) ? "-.->" : "-->");
+        out << (is_borrow_edge(e) ? "-.->" : "-->");
         out << " |" << escape(e.key) << "| ";
         edge_id = edge_counter;
         edge_counter += 1;
@@ -140,10 +183,11 @@ namespace rt::ui
         // Draw a new node
         nodes[dst] = {id_counter++, dst->is_opaque()};
         auto node = &nodes[dst];
+        auto markers = get_node_style(dst);
 
         // Header
         out << *node;
-        out << (dst->is_cown() ? "[[" : "[");
+        out << markers.first;
 
         // Content
         out << escape(dst->get_name());
@@ -151,8 +195,12 @@ namespace rt::ui
         out << (rt::core::globals()->contains(dst) ? " #40;global#41;" : "");
 
         // Footer
-        out << (dst->is_cown() ? "]]" : "]");
-        out << (reachable ? "" : ":::unreachable");
+        out << markers.second;
+        out
+          << (dst->is_immutable() ?
+                ":::immutable" :
+                (reachable && info->highlight_unreachable ? "" :
+                                                            ":::unreachable"));
         out << std::endl;
 
         result = node;
@@ -197,7 +245,7 @@ namespace rt::ui
         auto region = objects::get_region(dst);
         if (region != nullptr)
         {
-          region_strings[region].push_back(node->id);
+          regions[region].nodes.push_back(node->id);
         }
 
         return true;
@@ -216,64 +264,98 @@ namespace rt::ui
       }
     }
 
+    void
+    draw_region_body(objects::Region* r, RegionInfo* info, std::string& indent)
+    {
+      indent += "  ";
+      for (auto obj : info->nodes)
+      {
+        out << indent << "id" << obj << std::endl;
+      }
+      for (auto reg : info->regions)
+      {
+        draw_region(reg, indent);
+      }
+      indent.erase(indent.size() - 2);
+    }
+
+    void draw_region(objects::Region* r, std::string& indent)
+    {
+      auto info = &regions[r];
+      if (info->drawn)
+      {
+        return;
+      }
+      info->drawn = true;
+      auto depth = indent.size() / 2;
+
+      // Header
+      out << indent << "subgraph ";
+      out << "reg" << r << "[\" \"]" << std::endl;
+
+      // Content
+      draw_region_body(r, info, indent);
+
+      // Footer
+      out << indent << "end" << std::endl;
+      out << indent << "style reg" << r
+          << " fill:" << REGION_COLORS[depth % std::size(REGION_COLORS)]
+          << std::endl;
+    }
+
     void draw_regions()
     {
-      // Output any region parent edges.
-      for (auto [region, objects] : region_strings)
+      // Build parent relations
+      for (auto [reg, _] : regions)
       {
-        if (region->parent == nullptr)
-        {
-          continue;
-        }
-        if ((!info->draw_cown_region) && region->parent == objects::cown_region)
-        {
-          continue;
-        }
+        regions[reg->parent].regions.push_back(reg);
+      }
 
-        out << "  region" << region->parent << "  <-.-o region" << region
+      std::string indent;
+      if (info->draw_cown_region)
+      {
+        auto region = objects::cown_region;
+        out << "subgraph " << COWN_REGION_ID << "[\"Cown region\"]"
+            << std::endl;
+        draw_region_body(region, &regions[region], indent);
+        out << "end" << std::endl;
+        out << "style " << COWN_REGION_ID << " fill:" << REGION_COLORS[0]
             << std::endl;
-        edge_counter += 1;
       }
+      regions[objects::cown_region].drawn = true;
 
-      // Output all the region membership information
-      for (auto [region, objects] : region_strings)
+      if (info->draw_immutable_region)
       {
-        if ((!info->draw_cown_region) && region == objects::cown_region)
-        {
-          continue;
-        }
-
-        out << "subgraph ";
+        auto region = objects::immutable_region;
+        out << "subgraph " << IMM_REGION_ID << "[\"Immutable region\"]"
+            << std::endl;
+        draw_region_body(region, &regions[region], indent);
+        out << "end" << std::endl;
+        out << "style " << IMM_REGION_ID << " fill:" << IMMUTABLE_REGION_COLOR
+            << std::endl;
+      }
+      regions[objects::immutable_region].drawn = true;
 
-        if (region == objects::get_local_region())
-        {
-          out << LOCAL_REGION_ID << "[\"Local region\"]" << std::endl;
-        }
-        else if (region == objects::immutable_region)
-        {
-          out << IMM_REGION_ID << "[\"Immutable region\"]" << std::endl;
-          out << "  id0[nullptr]" << std::endl;
-        }
-        else if (region == objects::cown_region)
-        {
-          out << COWN_REGION_ID << "[\"Cown region\"]" << std::endl;
-          out << "  region" << region << "[\\" << region
-              << "<br/>sbrc=" << region->sub_region_reference_count << "/]"
-              << std::endl;
-        }
-        else
-        {
-          out << " " << std::endl;
-          out << "  region" << region << "[\\" << region
-              << "<br/>lrc=" << region->local_reference_count
-              << "<br/>sbrc=" << region->sub_region_reference_count << "/]"
-              << std::endl;
-        }
-        for (auto obj : objects)
-        {
-          out << "  id" << obj << std::endl;
-        }
+      // Local region
+      {
+        auto region = objects::get_local_region();
+        out << "subgraph " << LOCAL_REGION_ID << "[\"Local region\"]"
+            << std::endl;
+        draw_region_body(objects::cown_region, &regions[region], indent);
         out << "end" << std::endl;
+        out << "style " << LOCAL_REGION_ID << " fill:" << REGION_COLORS[0]
+            << std::endl;
+      }
+      regions[objects::get_local_region()].drawn = true;
+
+      // Draw all other regions
+      for (auto reg : regions[nullptr].regions)
+      {
+        draw_region(reg, indent);
+      }
+      for (auto reg : regions[objects::cown_region].regions)
+      {
+        draw_region(reg, indent);
       }
     }
 
@@ -318,24 +400,6 @@ namespace rt::ui
         out << "class " << *node_info << " error;" << std::endl;
       }
     }
-
-    void draw_info()
-    {
-      auto globals = rt::core::globals();
-      auto local_ctn = objects::DynObject::get_count() - globals->size();
-
-      // Header
-      out << "subgraph info" << std::endl;
-      out << "  i01[";
-
-      // Info
-      out << "Locals: " << local_ctn << "<br/>";
-      out << "Globals: " << globals->size() << "<br/>";
-
-      // Footer
-      out << "]" << std::endl;
-      out << "end" << std::endl;
-    }
   };
 
   MermaidUI::MermaidUI()
@@ -440,6 +504,7 @@ namespace rt::ui
   {
     // Make sure ui doesn't pause
     steps += 10;
+    highlight_unreachable = false;
 
     // Construct message
     std::stringstream ss;
diff --git a/tests/cowns/valid_01.vpy b/tests/cowns/cown1.vpy
similarity index 99%
rename from tests/cowns/valid_01.vpy
rename to tests/cowns/cown1.vpy
index da22a09..121ea1b 100644
--- a/tests/cowns/valid_01.vpy
+++ b/tests/cowns/cown1.vpy
@@ -4,7 +4,6 @@ global = {}
 a = Region()
 a.b = {}
 
-
 c01 = cown(move a)
 
 # Store the cown in a global
diff --git a/tests/cowns/valid_02.vpy b/tests/cowns/cown2.vpy
similarity index 94%
rename from tests/cowns/valid_02.vpy
rename to tests/cowns/cown2.vpy
index 82940ac..fc3d67e 100644
--- a/tests/cowns/valid_02.vpy
+++ b/tests/cowns/cown2.vpy
@@ -7,7 +7,7 @@ drop x
 
 def add_cown(obj, name):
     a = Region()
-    a.name = name
+    a.name = {}
     obj[name] = cown(move a)
 
 add_cown(global, "c1")
diff --git a/tests/cowns/invalid_child_region.vpy b/tests/cowns/invalid_child_region.vpy
new file mode 100644
index 0000000..3c1e276
--- /dev/null
+++ b/tests/cowns/invalid_child_region.vpy
@@ -0,0 +1,8 @@
+# Creating a region
+r1 = Region()
+r2 = Region()
+
+r2.child = r1
+
+# Error due to invalid LRC
+co = cown(move r1)
diff --git a/tests/cowns/invalid_not_bridge.vpy b/tests/cowns/invalid_not_bridge.vpy
new file mode 100644
index 0000000..10a7905
--- /dev/null
+++ b/tests/cowns/invalid_not_bridge.vpy
@@ -0,0 +1,7 @@
+# A simple region
+a = Region()
+a.b = {}
+
+# Error: Only the bridge object can be used for cown construction
+b = a.b
+c01 = cown(move b)
diff --git a/tests/cowns/invalid_shared_region.vpy b/tests/cowns/invalid_shared_region.vpy
index 7966208..e4f0dfb 100644
--- a/tests/cowns/invalid_shared_region.vpy
+++ b/tests/cowns/invalid_shared_region.vpy
@@ -1,8 +1,9 @@
 # Creating a region
 a = Region()
+a.v = {}
 
 # LRC = 2
-r01 = a
+r01 = a.v
 
-# Error due to invalid RC
-co = cown(take a)
+# Error due to invalid LRC
+co = cown(move a)
diff --git a/tests/region/fail_cross_region_reg.vpy b/tests/regions/fail_cross_region_ref.vpy
similarity index 100%
rename from tests/region/fail_cross_region_reg.vpy
rename to tests/regions/fail_cross_region_ref.vpy
diff --git a/tests/regions/region4.vpy b/tests/regions/region4.vpy
new file mode 100644
index 0000000..92da4a2
--- /dev/null
+++ b/tests/regions/region4.vpy
@@ -0,0 +1,30 @@
+# Create multiple regions
+r1 = Region()
+r1.level = "One"
+
+r2 = Region()
+r2.level = "Two"
+
+r3 = Region()
+r3.level = "Three"
+
+r4 = Region()
+r4.level = "Four"
+
+r5 = Region()
+r5.level = "Five"
+
+# Stack regions
+r1.n = move r2
+r1.n.n = r3
+
+r4.n = move r5
+r3.n = move r4
+drop r3
+
+# Move this into a cown
+c = cown(move r1)
+
+# Check the visuals
+mermaid_show_cown_region()
+mermaid_show_immutable_region()