From a passing glance, it simply looks like a large, overgrown hill. Step closer, and you’ll find the abandoned remnants of a once wild and wonderful waterpark.

Hidden in the brambles by Route 83 in Oakbrook Terrace, Illinois, you will find what is left of Ebenezer Floppen Slopper’s Wonderful Water Slides. When it first opened in 1980, the park had only two simple water slides. As it quickly grew into a major area attraction, the activities expanded, and the lines grew long.

Some of the slides involved sitting on rubber mats and going in groups, others entailed sliding down headfirst or atop an inner tube. A rubbery foam material lining the slides prevented people from injuring themselves against the walls. In 1987, adding bumps to the bottoms of the concrete slides transformed part of the park into “Doc River’s Roaring Rapids.”

The park came to a sudden close in 1989. No one knew why, and with decades of neglect and disuse, the once vibrant hotspot fell into eerie disrepair. Some of the slides are now decorated in graffiti, while others have become home to a variety of insects and animals. Interestingly, Ebenezer Floppen Slopper’s has returned to its original state of being—before any of the slides came about, the property was actually a landfill.

Technically called a cold-fill, and back before the days of stricter environmental regulation, the place held non-methane-emitting waste. In the 1960s it was known locally as “Mt. Trashmore.” When the dump filled up to ground level, it was shut down and covered with concrete, brick, and clay and was soon overgrown with grass and weeds. It wasn’t until the late 1970s, when a man named Mark Collor spotted the hill along Illinois 83, that the seed of the water park was planted.

Nowadays, though you won’t have much luck with the water slides, the undergrowth of Ebenezer Floppen Slopper’s Wonderful Water Slides provides a new type of adventure.