The Grimsel Test Site (GTS) is located at an altitude of 1730 metres in the granitic rock of the Aar Massif in 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.

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


Visiting the Grimsel Test Site

Visitors at the GTS

Groups are welcome to visit from Monday to Friday - pre-booking by registration is required. The Test Site is also open for group visits on occasional Saturdays.

Visits are possible from June to the middle of October. The tour of the facilities takes around 2 hours and is free of charge.

Contact / Registration:

Andrea Wettstein – De Marco
Hardstrasse 73
CH 5430
Tel + 41 (0)56 437 1310
This email address is being protected from spambots. You need JavaScript enabled to view it.