The greater Helsinki area is
supplied with drinking water via the Päijänne water tunnel.
With a
length of 120 kilometres, it is the longest continuous rock tunnel in
the world.
The constant temperature conditions found deep in the bedrock
maintains the water´s good quality.
The tunnel is excavated at a depht
of 30 - 100 metres in the bedrock.
It is built in 1973 - 1982 and
rebuilt in 2001.