Urban exploration (often shortened as UE, urbex and sometimes known as roof-and-tunnel hacking) is the exploration of man-made structures, usually abandoned ruins or not usually seen components of the man-made environment. Photography and historical interest/documentation are heavily featured in the hobby and, although it may sometimes involve trespassing onto private property, this is not always the case. Urban exploration may also be referred to as draining (a specific form of urban exploration where storm drains or sewers are explored), urban spelunking, urban rock climbing, urban caving, or building hacking.
