Abandonments

Ventures into abandoned structures are perhaps the most common example of urban exploration. Many sites are entered first by locals and may have graffiti or other kinds of vandalism, while others are better preserved. Although targets of exploration vary from one country to another, high-profile abandonments include amusement parks, grain elevators, factories, power plants, missile silos, fallout shelters, hospitals, asylums, prisons, schools, outmoded and abandoned skyscrapers, poor houses, and sanatoriums.

In Japan, abandoned infrastructure is known as haikyo (廃墟) (literally "ruins"), and the term is synonymous with the practice of urban exploration.^[7] Haikyo are particularly common in Japan because of its rapid industrialization (e.g., Hashima Island), damage during World War II, the 1980s real estate bubble, and the 2011 Tōhoku earthquake and tsunami.^[8]

In Bosnia and Herzegovina, a large underground facility abandoned since 1992 is Željava Air Base, situated under the Plješevica mountain, near the city of Bihać. It was the largest underground airport and military air base in the SFR Yugoslavia, and one of the largest in Europe. The complex contains tunnels in total length of 3.5 km (2.2 mi), and other large facilities. Nowadays, it is popular for urban exploration, although it is risky due to the possibility of anti-personnel landmines being located in unexplored areas, remnants from 1990s Bosnian War.^[9][10][11]

Many explorers find the decay of uninhabited space profoundly beautiful, and some are also proficient freelance photographers who document what they see, such as those who document the infrastructure of the former USSR.^[12]

Abandoned sites are also popular among historians, preservationists, architects, archaeologists, industrial archaeologists, and ghost hunters.

Active buildings

Another aspect of urban exploration is the practice of exploring active or in use buildings, which includes gaining access to secured or "member-only" areas, mechanical rooms, roofs, elevator rooms, abandoned floors, and other normally unseen parts of working buildings. The term "infiltration" is often associated with exploring active structures. People entering restricted areas may be committing trespass, and civil prosecution may result.

Catacombs

Catacombs such as those found in Paris,^[13] Rome, Odessa, and Naples have been investigated by urban explorers. Some consider the Mines of Paris, comprising many of the tunnels that are not open to public tours, including the catacombs, the "Holy Grail" due to their extensive nature and history. Explorers of these spaces are known as cataphiles.

Sewers and storm drains

Entry into storm drains, or "draining", is another common form of urban exploration. Groups devoted to the task have arisen, such as the Cave Clan in Australia. Draining has a specialized set of guidelines, the foremost of which is "When it rains, no drains!", because the dangers of becoming entrapped, washed away, or killed increase dramatically during heavy rainfall.

A small subset of explorers enter sanitary sewers. Sometimes they are the only connection to caves or other subterranean features. Sewers are among the most dangerous locations to explore owing to the risk of poisoning by buildups of toxic gas (commonly methane, hydrogen sulfide, or carbon dioxide). Sewers can contain viruses, bacteria, protozoa, and parasitic worms. Protective equipment is recommended for people who enter sewers.^[14]

Transit tunnels

Exploring active and abandoned subway and railway tunnels, bores, and stations is often considered trespassing and can result in civil prosecution due to security concerns. As a result, this type of exploration is rarely publicized. An exception to this is the abandoned subway of Rochester, New York, the only American city with an abandoned subway system that was once operational. The Cincinnati subway is also abandoned but was never completed. London has a number of stations on the London Underground network that have been closed over the years, with Aldwych tube station a popular location for explorers.

Utility tunnels

Universities, and other large institutions, such as hospitals, often distribute hazardous superheated steam for heating or cooling buildings from a central heating plant. These pipes are generally run through utility tunnels, which are often intended to be accessible solely for the purposes of maintenance. Nevertheless, many of these steam tunnels, especially those on college campuses, have a tradition of exploration by students. This practice was once called "vadding" at the Massachusetts Institute of Technology, but students there now call it roof and tunnel hacking.

Some steam tunnels have dirt floors, poor lighting and temperatures above 45 °C (113 °F). Others have concrete floors, bright light, and more moderate temperatures. Most steam tunnels have large intake fans to bring in the fresh air and push the hot air out the back, and these may start without warning. Most active steam tunnels do not contain airborne asbestos, but proper breathing protection may be required for other respiratory hazards. Experienced explorers are very cautious inside active utility tunnels since pipes can spew boiling hot water or steam from leaky valves or pressure relief blow-offs. Often there are puddles of muddy water on the floor, making slips and falls a special concern near hot pipes.

Steam tunnels have generally been secured more heavily in recent years due to their frequent use for carrying communications network backbone cables, increased safety and liability concerns, and perceived risk of use in terrorist activities.

Injuries and deaths