Urban exploration

Urban exploration is the name sometimes used for the act of exploring abandoned or rarely used buildings, tunnels, storm drains, rooftops, and other areas not designed for public use.

At MIT the exploration of steam tunnels is known as hacking or vadding. Another name for the hobby is infiltration, which is also the name of "the zine about going places you're not supposed to go". Note however that the term "urban exploration" generally refers to the exploration of abandoned, subterranean or otherwise unwelcoming environments, whereas "infiltration" more often is used to describe exploration of active buildings via stealth or disguise.