So even a veteran like Duncan is quick to point out the risks of urban exploration.

BBC: Discovering an unseen urban underworld

Urban exploration, or urban spelunking, has become a blanket term for the act of adventuring to normally unseen parts of a city.

BBC: Abandoned New York City

Still, urban exploration remains a popular pastime, as it can be done in any manmade environment anywhere in the world.

BBC: Discovering an unseen urban underworld