We will start building the room in Gazebo, save into Semantic Description Format (SDF), and insert in the Gazebo environment.

Launch Gazebo with Chefbot robot in an empty world:

    $ roslaunch chefbot_gazebo chefbot_empty_world.launch

It will open the Chefbot model in an empty world on Gazebo. We can build the room using walls, windows, doors, and stairs.

There is a Building Editor in Gazebo. We can take this editor from the menu
Edit | Building Editor. We will get an editor in Gazebo viewport.

We can add walls by clicking the Add Wall option on the left side pane of Gazebo.
In the Building Editor, we can draw the walls by clicking the left mouse button.
We can see adding walls in editor will build real 3D walls in Gazebo. We are building a similar layout of the room that we tested for the real robot.

Save the room through the Save As option, or press the Done button; a box will pop up to save the file. The file will get saved in the .sdf format. We can save this example as final_room.

After saving the room file, we can add the model of this room in the gazebo model folder, so that we can access the model in any simulation.