Monstropolis is a fictional city from the animated film series Monsters, Inc.. It is inhabited by various types of monsters who work in different industries, primarily focused on generating energy from children's screams. The city features a vibrant and colorful environment, with buildings designed to resemble the unique characteristics of its monster residents. The main workplace in Monstropolis is the Monsters, Inc. factory, where monsters like Sully and Mike Wazowski collect screams through doors that lead to the human world. The city operates on a system that transforms these screams into energy, highlighting the importance of laughter and fear in the lives of its inhabitants.