diff --git a/worlds/walls.sdf b/worlds/walls.sdf
index d56f351..7a9d75a 100644
--- a/worlds/walls.sdf
+++ b/worlds/walls.sdf
@@ -166,18 +166,6 @@
     <model name="ground_plane">
       <static>true</static>
       <link name="link">
-        <inertial>
-          <inertia>
-            <ixx>0.16666</ixx>
-            <ixy>0</ixy>
-            <ixz>0</ixz>
-            <iyy>0.16666</iyy>
-            <iyz>0</iyz>
-            <izz>0.16666</izz>
-          </inertia>
-          <mass>10</mass>
-          <pose>0 0 0 0 0 0</pose>
-        </inertial>
         <collision name="collision">
           <geometry>
             <plane>
@@ -224,21 +212,47 @@
       <pose>0 0 0 0 -0 0</pose>
       <self_collide>false</self_collide>
     </model>
+    <light name="sunUTC" type="directional">
+      <pose>0 0 500 0 -0 0</pose>
+      <cast_shadows>true</cast_shadows>
+      <intensity>1</intensity>
+      <direction>0.001 0.625 -0.78</direction>
+      <diffuse>0.904 0.904 0.904 1</diffuse>
+      <specular>0.271 0.271 0.271 1</specular>
+      <attenuation>
+        <range>2000</range>
+        <linear>0</linear>
+        <constant>1</constant>
+        <quadratic>0</quadratic>
+      </attenuation>
+      <spot>
+        <inner_angle>0</inner_angle>
+        <outer_angle>0</outer_angle>
+        <falloff>0</falloff>
+      </spot>
+    </light>
+    <spherical_coordinates>
+      <surface_model>EARTH_WGS84</surface_model>
+      <world_frame_orientation>ENU</world_frame_orientation>
+      <latitude_deg>47.397971057728974</latitude_deg>
+      <longitude_deg> 8.546163739800146</longitude_deg>
+      <elevation>0</elevation>
+    </spherical_coordinates>
     <model name="box1">
-      <pose>5 0 0 0 0 0</pose>
+      <pose>5 0 7.5 0 0 0</pose>
       <static>true</static>
       <link name="link1">
       <collision name="collision">
         <geometry>
           <box>
-            <size>1 20 30</size>
+            <size>1 20 15</size>
           </box>
         </geometry>
       </collision>
       <visual name="visual">
         <geometry>
           <box>
-            <size>1 20 30</size>
+            <size>1 20 15</size>
           </box>
         </geometry>
         <material>
@@ -251,19 +265,19 @@
     </model>
     <model name="box2">
       <static>true</static>
-      <pose>-3 5 0 0 0 0</pose>
+      <pose>-3 5 7.5 0 0 0</pose>
       <link name="link2">
       <collision name="collision">
         <geometry>
           <box>
-            <size>10 1 30</size>
+            <size>10 1 15</size>
           </box>
         </geometry>
       </collision>
       <visual name="visual">
         <geometry>
           <box>
-            <size>10 1 30</size>
+            <size>10 1 15</size>
           </box>
         </geometry>
         <material>
@@ -276,19 +290,19 @@
     </model>
     <model name="box3">
       <static>true</static>
-      <pose>13 -10 0 0 0 0</pose>
-      <link name="link2">
+      <pose>13 -10 7.5 0 0 0</pose>
+      <link name="link3">
       <collision name="collision">
         <geometry>
           <box>
-            <size>17 1 30</size>
+            <size>17 1 15</size>
           </box>
         </geometry>
       </collision>
       <visual name="visual">
         <geometry>
           <box>
-            <size>17 1 30</size>
+            <size>17 1 15</size>
           </box>
         </geometry>
         <material>
@@ -300,20 +314,20 @@
       </link>
     </model>
     <model name="box4">
-      <pose>12 0 0 0 0 0</pose>
+      <pose>12 0 7.5 0 0 0</pose>
       <static>true</static>
-      <link name="link1">
+      <link name="link4">
       <collision name="collision">
         <geometry>
           <box>
-            <size>1 20 30</size>
+            <size>1 20 15</size>
           </box>
         </geometry>
       </collision>
       <visual name="visual">
         <geometry>
           <box>
-            <size>1 20 30</size>
+            <size>1 20 15</size>
           </box>
         </geometry>
         <material>
@@ -324,31 +338,5 @@
       </visual>
       </link>
     </model>
-    <light name="sunUTC" type="directional">
-      <pose>0 0 500 0 -0 0</pose>
-      <cast_shadows>true</cast_shadows>
-      <intensity>1</intensity>
-      <direction>0.001 0.625 -0.78</direction>
-      <diffuse>0.904 0.904 0.904 1</diffuse>
-      <specular>0.271 0.271 0.271 1</specular>
-      <attenuation>
-        <range>2000</range>
-        <linear>0</linear>
-        <constant>1</constant>
-        <quadratic>0</quadratic>
-      </attenuation>
-      <spot>
-        <inner_angle>0</inner_angle>
-        <outer_angle>0</outer_angle>
-        <falloff>0</falloff>
-      </spot>
-    </light>
-    <spherical_coordinates>
-      <surface_model>EARTH_WGS84</surface_model>
-      <world_frame_orientation>ENU</world_frame_orientation>
-      <latitude_deg>47.397971057728974</latitude_deg>
-      <longitude_deg> 8.546163739800146</longitude_deg>
-      <elevation>0</elevation>
-    </spherical_coordinates>
   </world>
 </sdf>