This is an example office world in Gazebo. You need to delete build folder and follow these steps to run in Gazebo
sudo apt-get update
sudo apt-get upgrade -y
cd ~/Gazebo-office-model
mkdir build
cd build/
cmake ../
make
export GAZEBO_PLUGIN_PATH=${GAZEBO_PLUGIN_PATH}~/Gazebo-office-model/build
cd ~/Gazebo-office-model/world/
gazebo world