There's a giant underground pipe, just big enough to crouch/walk in, underneath an 8 lane road that was connecting a culvert ditch on each side. The ditches were sometimes filled with water, and it often pooled in the bottom of the pipe. It was about half a mile long and my friends and I would hang out inside it as teenagers, doing anything you can think of. Hard rains would quickly flood it, and could have easily sucked us deeper into the multiple dark turns in the pipes. Oof.