Although a country with few people and plenty of space, Finlands’  capitol city Helsinki being located on a peninsula finds itself constantly constrained by the sea for space. Luckily the city sits above bedrock which is deep and which frequently punctures the ground. So Helsinki increasingly uses its bedrock to tunnel into and create an underground city. Now with over 400 documented underground facilities and 200 more planned, Subterranea Helsinki is probably one of the largest and most comprehensive underground city systems in the world for its size.

Helsinki Underground Masterplan above for full size image go here.

(key:blue is planned underground space and grey is existing, orange is possible future)

Underground churches, gyms, ice hockey pitches, running tracks, water processing plants, shopping malls, bus stations the list goes on and on. Infact according to regulations buildings over a certain size must provide some sort of bomb shelter, it’s often unavoidable not to build underground.

Probably the best known underground areas are around Central Station which is home to a network of metro stations shops and tunnels that connect much of the city centre together and allow you to arrive and move through the centre of the city without surfacing at all. Also because when new facilities are built they are connected back into the existing underground system it expands out like the roots of a tree. A good example of this is round Kaisaniemi metro which links underground station with shopping mall within an existing building that joins up to an atrium made from a filled in urban block which in turn links through to an underground cinema. Here the underground city tunnels back into the urban fabric above ground also.

I think this is one of the most impressively urban things about Helsinki which otherwise is a quite a centrally planned and unobtrusive small city. This ‘deep urbanism’  is where Helsinki distinguishes itself as being different, and the fact that the city has an official underground city plan reflects this attitude to some degree.

I hope that the new harbour redevelopment includes for some sizeable public facilities underground that can continue to expand the city below ground too.

Central Station underground

Below are a list of some the larger underground structures in Helsinki:

Temppeliaukio Church

Temppeliaukio Church was built into solid rock in 1969. One of the better modern buildings in Helsinki. The sides of the church let water through on purpose when it rains allowing for natural water flows down the side of the church.

Itäkeskus underground swimming centre

The underground swimming centre was carved into bedrock in 1993. The spa-type underground space contains a 50-metre swimming pool, whirlpool baths, saunas, a gym, etc. The facility can be converted into a shelter for 3,800 persons.

Viikinmäki underground wastewater treatment plant

Helsinki Water has centralised all of its wastewater treatment operations into the Viikinmäki wastewater treatment plant. The total volume of excavated rock was 1,200,000 m3. The first phase (1,000,000 m3) was excavated in 1988-91 and the second phase (200,000 m3) in 2000-01.

Otaniemi – underground spaces
Over 50 underground spaces, including the national film archives, the underground shelters of the Dipoli conference centre and VTT Technical Research Centre of Finland, Helsinki University of Technology campus area connection tunnels, Laboratory of Rock Engineering test tunnel, etc.

Western metro expansion
Länsimetro is 13.9-km long twin tunnel and 7 new stations. Construction is estimated to start in late 2009 and the project is expected to last four years at most. The westbound metro line will be completly underground

KEHU – Helsinki Service tunnel

2.5-km service tunnel across the city, from east to west, under the historical centre of Helsinki. Construction scheduled for 2006-10. The tunnel will be used to service shops, restaurants, offices and hotels in the area.

Underground coal storage and district cooling
Helsinki Energy’s underground coal storage facility in Salmisaari was built in 2001-03. The project also included an underground district cooling centre, a power station and 3.5 km of tunnels. The total excavated volume was 550,000 m3. Each coal silo is 65 metres high and has a 40-metre diameter with a circular plan cross-section. The volumetric capacity of each silo is 81,000 m3.

Airport transit (Kehärata)
Airport transit is a new rail section connecting the city centre to Vantaankoski local track with the main northbound rail track. The whole project consists of 18 km of new double track and 8 new stations. Of this, 8 km of track and 4 stations will be fully underground.

Päijänne Water Tunnel

The Worlds’ second longest continuous Rock Tunnel which brings fresh water from Lake Päijänne to Helsinki. (wikipedia / homepage)

District Heating System

The whole city has a district heating system which supplies over 90% of Helsinki’s heating requirements. This system is supported by a massive underground tunnel network of more than 40 km of multi-utility  tunnels.

Hartwall Arena

Subterranean full size ice hockey hall

Suomenlinna Tunnel

See the excellent post at Locating Helsinki about this. A service tunnel that connects one of Helsinki’s most important islands to the mainland. There has been talk about expanding the metro here one day.

Crazy Ideas:

Helsinki Tallinn tunnel

References:

WTC

Helsinki Underground City

rumors

helsinki underground masterplan

Finnish Tunneling Association

My Helsinki Subterranea flickr set