A new Swiss test-site for avalanche experiments has been built to study the overall dynamic behaviour of dense-flow and powder-snow avalanches and to measure avalanche impact forces along their path. An important application of the data gathered is for the verification and calibration of physical models and of computer simulation programs. For the impact studies, a wall, a pylon of circular section, a girder mast and a section of the roof of a road protection gallery are placed within the avalanche track and equipped with force transducers and pressure and strain gauges. The dynamic behaviour of the avalanches is measured by Doppler- and FMCW-radars. Snow mass balances are established by photogrammetry. The avalanches are artificially released. For many years, the Swiss Federal Institute for Snow and Avalanche Research used a test-site in the Canton Grison to study the dynamic behaviour of dense-flow avalanches. The limited number of successful experiments at this site forced the institute to examine several alternatives for an avalanche test-site. It was finally decided that a site in the Canton Valais, with several potential avalanche tracks with more than 1000 m of potential difference in altitude, was most suitable for our purpose. After several years of planning for the test-site, the civil engineering construction work started in summer 1997, followed by the installation of sensor devices and the data acquisition, transfer and storage system. In December 1997, the test-site was ready for experiments.