Is a mountain tunnel in Bragernesåsen, opened in 1961 when Drammen celebrated its 150th anniversary.
With six spirals, the tunnel goes through a massive of eruptive rock (granite porphyry below, basalt above), ending at Nedre Skanse, formerly called Breidablikk.
The tunnel is 1650 metres long, 9 metres wide and originally had a height of 3.1 metres but it was extended later and today also large, modern touring coaches can pass.
The rise is from 20 to 213 metres above sea level with a gradient of one in ten, and each spiral has a 70 metre diameter.
Shortly after the turn of the century, the Spiralen started as an open quarry to provide road construction with materials. It was the city engineer Eivind Olsen's idea that the quarry could be developed into a spiral tunnel up through Bragernesåsenand this work commenced in 1953 after 70,000 cubic metres of rock had been blasted off. The road has been tolled from the beginning except for the period of 1987-1994.