Underground works


 * For mines and quarries see Mining tourism, for natural underground structures see Caves.

Underground works are a travel destination of interest to a number of travellers.

Understand
Humans have been digging holes and underground structures since prehistory.

As well as expanding natural caves, humans have constructed or expanded countless works of their own efforts underground from early residences of prehistory through to contemporary tubes and tunnels that support a modern lifestyle, or for disposal of its wastes.

A number of underground structures were built for warfare, be it tunnels under enemy positions or underground fortresses and anything from simple subsurface storage rooms through to the hardened bunkers built for a "day after" – which thankfully never arrived.

Amongst the other underground works are the subterranean grottoes, and passages of those with both the eccentricity, finance and folly to construct them.

Other Underground works however were built to aid the flow of trade and people, be it road, river or rail, going underground made sense to the engineers of history when the surface way was congested or impractical to the demands. In some regions the pressure for improved communication and transport has meant the same mountain have got more tunnels at increasingly lower levels, making for so called "base tunnels".

Get in
The easiest underground works to access are those which were clearly designed as public spaces or where tourist facilities have been installed specifically to aid access by visitors. Not all underground works are open to the traveller even on organized tours.

A number of cities have vast underground public spaces, such as Japan's underground shopping malls, or Houston's tunnel system. In other cities railway stations are partly or entirely under ground. Leipzig for instance has underground through tracks beneath its multilevel shopping mall/terminus railway station.

Urban rail
Many large cities have transit systems where the stations and tracks are below the surface, whose public areas can be accessed for the price of a standard fare. Some systems of particular note are London, New York, Paris, Berlin, Moscow, and the worlds longest art Gallery in Stockholm, but other systems are also of interest to transit fans.

Whilst some Urban Rail systems occasionally run limited enthusiast tours 'behind the scenes', the health and safety considerations of a working railway, the current 'security' climate in many regions, coupled with the confined operational environment, mean that these are rare, and typically take place outside operational periods. Specialist Enthusiast publications may advertise these type of tours, but booking early is essential owing to limited numbers.

Military sites
Military facilities – even if seemingly abandoned or out of use – often remain highly sensitive sites. An unexpected or unannounced visit could at best lead to a lengthy interrogation, with considerably worse outcomes depending ultimately on the mood of the personnel you encounter. You should make formal contact in writing with the relevant military authorities as soon as you have firm travel plans. Do not be disappointed if a planned or agreed visit has to be cancelled or curtailed for operational and security reasons, or if you are denied access without any reason at all being provided.

See
For the countless underground works resulting from mining or quarrying see Mining tourism.

See also Nuclear bunkers for cold-war bunkers ;Fortifications for other underground works connected with military projects; and Rail tunnels for railway tunnels.

France

 * The Mines of Paris often erroneously termed the Catacombs.
 * The Mines of Paris often erroneously termed the Catacombs.

Germany
During the second world war, constant allied bombardment which had destroyed several important military factories forced the Nazis to dig deep and hide their military infrastructure underground. Nazi architect and minister of armament Albert Speer was the leading force behind those efforts often brutally abusing and outright murdering the forced laborers used for those projects. While many of those structures were deliberately destroyed after the war, a few survive to this day and can be visited.

Italy

 * The First World War on the Alpine Front pitted Austria-Hungary against Italy and involved a lot of mines and tunnels, some of which are still visible a century later.

Japan

 * Metropolitan Area Outer Underground Discharge Channel in Kasukabe, Saitama prefecture is a monumental underground flood-control system finished in 2009. It was constructed to prevent damages caused by the perennial floods which have plagued this part of the Kanto plain. It is possible to book a tour underground.

Jordan

 * Petra

Korea




Norway

 * GaustatoppenFromAirplane.JPG

United Kingdom

 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.
 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.
 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.
 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.
 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.
 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.
 * A small number of Ice Houses associated with grand houses, remain in the UK. These were used prior to modern refrigeration to store the ice used by the house.

For less well known Underground works consider joining a specialist organization such as Subterranea Brittanica who specialize in the research of such sites.

Photos
If you are permitted to take simple photos, take them. You should however be aware that taking photos in low light will require a 'fast' sensor and a fast lens. Many shots will be easiest with a wide-angle lens. Seek appropriate local advice if you wish to use a flash.

Stay safe
There are few risks associated with underground works clearly adapted for tourism or intended as accessible public spaces, and if you have any doubts as to your ability or fitness (including mental attitude), sticking to these is very strongly recommended. Sites that have organized formal tours will also have established rules and procedures which should be adhered to.

In order to stay safe when visiting less accessible underground works, it is vital to know as much as possible about the specific sites you wish to visit, so that you can plan accordingly.

Underground works where access, up to and including the entrance, involves tight crawls, confined space, vertical drops, sharp climbs, any expanse or mass of water, or in general where a failure of any equipment is going to become a critical problem, are considered beyond the scope of accessibility for the non-specialist. For safety advice concerning visiting these less accessible works, specialist expertise will need to be sought from dedicated caving and subterranean exploration organizations, familiar with the specific site.

For other reasonably accessible underground works not as well adapted for the tourist or traveller (if at all), you should seek and heed local advice even if it seems easy at a cursory glance at the surface or entrance. Contacting the site's current (or former) operator in advance will also allow them to inform you of any known risks – but don't rely on them knowing or telling anything unless they take responsibility.

There is some detailed advice on cave safety at caves.org, which is also applicable to underground works. Some advice:


 * Know the works you wish to visit and your exit(s) before you enter, and if there is more than one entrance or exit, know which ones will be safe to use. Practically all responsible underground explorations are planned only after weeks or months of research.
 * Never enter underground works alone, because not only will there be no-one to get you out, but no-one will know where you are!
 * Your "smart" phone will have little or no service below ground. Some works use materials that by themselves will block or interfere with typical wireless communication.
 * It is best practice to follow the example of the professionals and visit in groups of at least four. As well as lodging plans with appropriate contacts, in nearly all circumstances a surface watchman is essential whose responsibility is to contact the authorities if things go bad or a group below the surface fails to return by a specified time.
 * Underground works are naturally dark, and without artificial light (which in disused or abandoned works you will have to provide yourself), you will have a hard time navigating them. Don't rely on a single light source, which could fail. Spare light sources are strongly recommended.
 * Check the weather first! A number of underground works are subject to flooding. In wet conditions water levels can change unexpectedly, limiting or cutting off access routes or even exits. In others the removal of flood or storm water is a primary function of the work concerned, and the water level in the system can change automatically within minutes. Getting caught out by rising water levels isn't worth it.
 * Disused facilities are not going to be well maintained, and fixed access equipment may well have been removed at abandonment, or has subsequently decayed beyond use.
 * Underground structures also need ventilation and drainage, without these, hazards such as bad air, or stagnant water can rapidly accumulate.
 * Do not under any circumstances enter any underground expanse or mass of water, without having in advance sought appropriate advice. Not only can the depth be deceptive, but the water may not be as pure as its appearance suggests. Caution should similarly be exercised in respect of moderate mud, silt, and fallen debris.
 * Whilst countless disused military facilities may seem abandoned, many of them are still nominally highly restricted sites, and unauthorized access to these will at the very least lead to a lengthy interrogation by the respective military authority. Also many civilian facilities are considered sensitive by their respective current or former operators, for safety and security reasons. If in any doubt, confirm your intended plans with the relevant authorities, site owners or operators well in advance.
 * In addition to dust, the local wildlife may not appreciate being unduly disturbed.

Respect


Be respectful of the underground environment you are visiting. Ideally you should try to leave the underground environment as you found it as far as possible. No garbage and human waste should be left behind. The very presence of human beings and light can also severely change the micro-climate in the underground environment, issues like Lampenflora or plants growing due to the light and warmth of artificial light sources being a serious problem in some underground structures.

If the Underground works are not generally accessible or don't operate formal tours, discreetly and politely seek the consent of the site's owners and operators first. Not only does this express your genuine interest in any given site, but will allow those familiar with the site to advise on specific procedures, taboos or prohibitions. Some site owners and operators may also be willing to provide additional information to place the site in context. Joining a specialist group, is also recommended.

Exceptional care must be exercised where unique historic (or prehistoric) cultural heritage exists, so that it is not lost or degraded to future generations. Some of these sites are associated with tragic historical events and others are literally the place where people died or were buried. Some underground structures may also be considered "holy ground" in a religious or secular sense, so behave accordingly.