The Old Industrial Park is a location visited in Marceline's past during "The Empress Eyes." It was showed in a flashback and was also a location where Marceline had set hobo camp. She explained that she was a vampire hunter during this period and saved a family from an attacking vampire in her song "Memories."
The Old Industrial Park has many abandoned departments such as a pantry, a sewage department and huge tubes that possibly carried water supply throughout the facility.
There is also a cilinder object with a skull possibly hinting signs of radioactivity and in general, there are leave-less tress, rocks and cars scattered everywhere. Marceline's hobo camp was also situated in this park.