According to legend, the hole was made by the troll Hestmannen while he was chasing the beautiful girl Lekamøya. As the troll realized he would not get the girl, he released an arrow to kill her, but the troll-king of Sømna threw his hat into the arrow's path to save her. The hat turned into the mountain with a hole in the middle. Also, Felice Vinci has linked the legends about Torghatten to the Homeric myth of Polyphemus.
The tunnel is 160 metres (520 ft) long, 20 metres (66 ft) wide, and 35 metres (115 ft) high. It was formed during the Scandinavian ice age. Ice and water eroded the looser rocks, while the harder ones in the mountain top have resisted erosion.