Speilsalen

Speilsalen (The Hall of Mirrors) was a natural glacial formation caused by a river underneath a glacier in the Trollheimen mountains in the municipality of Oppdal in Trøndelag county, Norway. It was located at the northeast base of the mountain Blåhøa.
Under favourable conditions late summer, it was possible to walk the from one end to the other underneath the glacier. It was never considered safe to walk under a glacier. Speilsalen collapsed in August 2007.