UE is not a crime per se, and most explorers do not see it as done to break laws, other than trespassing, which is merely a crime which is deemed necessary, and not as a malicious act.

This includes seeing secured or member-only areas, mechanical rooms, roofs, elevator rooms, and other normally unseen parts of such buildings. New York City probably has the largest number of subway explorers, although others exist in most major european cities, including London and Moscow.ДЄnother aspect of urban exploration is the practice of exploring active or in use buildings. As a result, subway exploration is usually the least publicised type of exploration. The penalties for getting caught in subway/underground railway tunnels are some of the strictest involved in this hobby. Sewers are among the most dangerous locations to explore, and those who explore them are often on the fringe of a group that's already on the fringe of society. Sometimes they are the only connection to caves or other subterranean feature. Draining has a specialized set of guidelines, the foremost of which is 'When it rains, no drains.'ДЄ small subset of explorers enters sanitary sewers.

Groups devoted to the task have arisen, such as the Cave Clan in Australia. Steam tunnels in general have been getting more secure in recent years, due to their use for carrying network backbones and mass hysteria over potential terrorism.Д®ntry into storm drains, or draining, is another common form of UE. This was once called vadding at MIT, though students there now refer to it as Roof and tunnel hacking. North American Universities that have steam tunnels often also have a tradition of steam tunnel exploration by students. These steam ducts are generally run through tunnels, which are often accessible to humans for the purposes of maintenance. Universities and other large institutions, such as Hospitals often distribute steam for heating buildings from a central heating plant (Boiler House).

Abandoned tunnels such as mines, headraces, tailraces, and rail tunnelsДЄctive tunnels include steam (such as those found under large building complexes with a central boiler), electricity, telephone, water, and other utility tunnels subway or Underground Railway and other transit tunnels and stormwater or sanitary sewers.

Explorers often focus on the natural decay, as nature grows trees on the roof and weeds in the carpet, and unnatural decay of the structure as scrappers, looters, squatters, and vandals demolish the building from the inside out.Д®xploration targets vary from one country to another, however some of the more common abandoned structures to explore include: Abandoned sites are generally entered first by locals, and often sport large amounts of graffiti and other vandalism. Ventures into abandoned structures are perhaps the most common example of UE. Urban explorers do any or all of these things, but often specialize on one or two. UE can further be separated into subcategories.

Urban explorer storm drain