Wiktionary
urban explorer
n. A person who explores restricted urban areas such as abandonments, tunnels, roofs, construction sites, etc. Certain non-urban sites can also count, such as mines, quarries, and grain/missile silos.
Wikipedia
Urban Explorer
Urban Explorer is a 2011 German horror- thriller film directed by Andy Fetscher. The film is about urban exploration in subterranean Berlin. Also known as "The Depraved".