Urbex, or Urban Exploring, is the exploration of abandoned and non-public urban locations.
Urbex is most commonly understood as the exploration of parts of cities that no-one visits, be it abandoned buildings, steam tunnels, metro systems, or even dangerous underground locations such as sewers. Infiltration, which involves exploring used/inhabited (but not necessarily public) areas, is often lumped in with urbex, but it tends to attract a different crowd. Virtually any building can be an infiltration "destination", but the most popular are architecturally interesting commercial buildings, industrial sites and hotels.
Whilst urbex has gained a notorious reputation of being illegal (such as requiring by definition trespassing), the bulk of exploration happens in places no-one cares about (which explains both their abandonment and/or the fact that no-one bothered to lock them up or even post a no trespassing sign). Although some urban exploration does indeed occur in areas that are legally off-limits, few "practitioners" would ever recommend that you do this.
However, many individuals and organizations involved in the genuine research, documentation and recording of older (and abandoned) buildings, works and infrastructure strongly advocate against "casual" urbex, preferring that those who are interested join specialist organizations that have built up appropriate access procedures and goodwill with site owners.
Novelty, thrill seeking, boredom, and photography are the main reasons urbex expeditions occur. Urbex opens up a whole new field of sightseeing, and makes for good stories. Many explorers find the forgotten, abandoned, and otherwise undiscovered places to have a certain beauty not to be found elsewhere—hence the popularity with photographers and fans of architecture. Infiltration is popular too for thrill seeking, but is more valued for aesthetic and other pleasures that would otherwise be off-limits. Visitors to ghost towns and abandoned structures inevitably wonder what these places must have been like in their heyday.
Especially in big cities, evacuated buildings get scheduled for demolition. These might draw interest, especially by photographers, for a last chance to see them standing.
Urbex sites exist almost anywhere in the world. However, as a general rule, the interesting nature of a site will be based on a few key factors:
The Cold War from 1945 to 1991 left behind military installations, bomb shelters and a partly fortified border called the Iron Curtain.
The decline of public transportation since the 1950s, and the decline of heavy manufacturing since the 1970s have left many American cities with lots of abandoned infrastructure dating back to those eras, particularly in what is today called the "Rust Belt", comprising most of the Midwest and parts of the Mid-Atlantic region.
As abandoned sites, by their nature, are not kept up by anyone, it is essential that an urbexer leave them as they are found for the next visitor to prevent a slow but steady decay. That means:
Some sites, whose locations often but not always remain a closely guarded secret, are contenders for future historical preservation, or in a few odd cases even potential UNESCO World Heritage rating. Archaeological sites often omit specific location from their public entries on historic registers to prevent the historical record from being damaged or destroyed.
If you are exploring an abandoned business or theme park, then a single business card or flyer (in cases only when there is an entire room full of them: more common than you'd think) is sometimes deemed an exception to this rule by specific urbexer enclaves, but not by the broader community as it can constitute theft. Plus, for a popular site, that room full of discarded cards—a bizarre sight in itself -- can whittle down very rapidly.
This is largely the reason why giving out maps and directions to a site in public is taboo within the community. Unless the experienced urbexer has been able to meet, talk to, and sufficiently understand the potential recipient of information, there is no way to ensure that they are not a vandal or treasure hunter. It only takes a single undignified urbexer to at best, ruin a site, at worst, erase a piece of history.
For photographers annotating photographs, in keeping with this guideline, the norm is to just state the name (often an exonym) for the site and details down to country or sometimes state/province/prefecture level. For sites of extraordinary historical value or fragility, and little fame, no detail apart from an exonym is the norm.
Take only photographs, leave only footprints, and avoid the latter if you can.
Safety is or should be the number one preoccupation of any exploration. Urbex trips are often fraught with danger. Abandoned buildings or entire ghost towns are abandoned for a reason. Decrepit floors and stairs might collapse under your weight, a brush against rusty metal could give you tetanus, you might run into a gang that's been playing around in the place, encounters with wild animals, etc. Another risk in old buildings is the use (or disturbance) of materials whose use is for good reason no longer allowed, asbestos and lead (in paint) being two specific examples. On the upside, law enforcement is unlikely to care too much about your being there. At worst you would probably get a fine, and be allowed to walk out on your own.
Underground urbex suffers from several physical threats—again, crumbling infrastructure can be your enemy, as well as resident weirdos and animals, but there are extra dangers from steam vents, electricity, flash floods, and poisonous gases. Make sure you know what you are doing. Abandoned mines are a particularly dangerous maze of cramped, dark tunnels with sections submerged in water and vertical shafts dropping 60 metres or more. Rock may be crumbling; wooden structures which once supported the tunnels may be rotting. Cave-ins, falls, contaminated mine water and poisonous gas are hazards.
Danger from law enforcement has increased exponentially in the United States and several other countries following major terrorist attacks. If you are found on camera to be sneaking around subway tunnels, you may find yourself arrested on suspicion of terrorist activity: that's far worse than a fine for trespassing!
A good place to check for legal dangers is to review details of your intended country's freedom to wander.
There are universally recommended steps to keep yourself safe while exploring, and you would be a fool not to follow them. Don't ever do this alone. Make sure that someone else knows what you are doing, and plan to check in with them at set times. Bring a phone, light source with multiple batteries, hard hat if appropriate, heavy duty boots, and some water and food. If trying something new, do research first either on the chosen site, or at least on the type of site... and lastly, if it rains, no drains!
Wandering around non-public or otherwise off-limits area of otherwise inhabited sites or buildings (without authorization or consent) may entail far less physical danger, but an exponentially increased chance of discovery and trouble with law enforcement, site operators or other authorities.
Government buildings, airports, sea-ports, as well as rail and transit infrastructure (examples being tracks, depots, rail-yards, plant rooms and car-sheds), are exceptionally paranoid due to ongoing threats from terrorism. You will end up in jail (potentially for an extended period) if discovered. In some countries and even some specific sites, it is worth considering individual staff, law enforcement, and "security" can be very direct in ensuring the integrity of their sites.
Industrial sites have also become quite paranoid.
Staff and "security" can also be somewhat direct in respect of hotels and commercial buildings, even if the concerns are motivated by more concerns about potential criminal intent, than ongoing terrorism concerns. Whilst many may respond with a demand to leave the building or a request to pay a fine, others will have no hesitation in calling law enforcement.
Even in heavy-traffic areas which are clearly open to the public (such as banks and subway/metro stations), you may be challenged if you attempt to take photographs, or make notes about certain things.
Abandoned buildings might be claimed by squatters, homeless people and even criminals, who see explorers as intruders.
Access All Areas - Ninjalicious, the widely-accepted "definitive" guidebook to urbex, including sections on theory, technique, safety and ethics.
Related: Travel photography
Related: Industrial tourism