The Grimsel Test Site (GTS) is located at an altitude of 1730 metres in the granitic rock of the Aar Massif in central Switzerland. It lies at a depth of around 450 metres beneath the surface and is reached by an access tunnel belonging to the Kraftwerke Oberhasli AG (KWO), the local hydro-power company.

The GTS tunnel system is around one kilometre long and was excavated in 1983 using a full-face tunnelling machine (diameter 3.5m). The Test Site offers ideal conditions for carrying out a wide range of test programmes. (Please see the Visit the GTS section for details on visiting the GTS.)

Location of the Grimsel Test Site in Switzerland Location of the Grimsel Test Site (GTS) in Switzerland - (1) Grimsel Test Site, (2) Rätrichsbodensee, (3) Grimselsee and (4) Juchlistock

Location of the Grimsel Test Site in the Grimsel Pass

Tunnel Layout

Main project locations are shown below.

Grimsel tunnels 2015