Have you ever been intrigued by an abandoned building or decaying, empty lot? Urban exploration is all about exploring the man-made landscape, from buildings and tunnels to sewers, often photographing them [source: Barkham]. Because it often involves entering private property without the owner's permission, urban exploration can land you in jail.
Urban exploration crosses over to the illegal when explorers break into abandoned buildings to check them out without permission. It can be very dangerous, and not just because old buildings and tunnels can be structurally unsound. Because these old structures haven't been maintained, urban explorers put themselves at risk of coming into contact with contaminants like free asbestos and biohazards. The Ohio Exploration Society Web site has some handy tips on how to explore urban areas more safely.
Urban explorers also sometimes head underground for photo opportunities. This practice, called "drainboating" is basically subterranean urban exploring -- on a boat! Drainboaters make their way into underground tunnels and sewer systems with small, inflatable boats, then float through the underbelly of a city.
Not all urban exploration is illegal. Some consider visiting poorly-maintained historic sites urban exploration. It's all about witnessing and documenting the beauty of decay. You can also find out who owns the building or contact local authorities and request permission to enter the building or even ask for a tour [source: Ebaster].