Urban exploration is the exploration of manmade structures, usually abandoned ruins or hidden components of the manmade environment. Photography and historical interest/documentation are heavily featured in the hobby, sometimes involving trespassing onto private property. Urban exploration is also called draining, urban spelunking, urban rock climbing, urban caving, building hacking, or mousing.

Roof and tunnel hacking is the unauthorized exploration of roof and utility tunnel spaces. The term carries a strong collegiate connotation, stemming from its use at MIT and at the U.S. Naval Academy, where the practice has a long history. It is a form of urban exploration.