Wikipedia
Gråkallen
Gråkallen is a mountain in the Bymarka area in the municipality of Trondheim in Sør-Trøndelag county, Norway. The tall mountain is located in the Byåsen part of the city of Trondheim.
The summit is covered by an abandoned fenced military installation. Below the summit (on the col to the right of the summit above the lake) there is a ski station where buses from Trondheim will set you down. In the summer, the ski runs through the pine forests make for perfect hiking and mountain biking back to the city below.