Potentially the most famous pass in Switzerland, the old Tremola road takes you up almost 900 meters from the valley town of Airolo to the top of Passo San Gottardo (Gotthard pass for the German and English speakers out there). The start of the climb is laid with pristine tarmac and is mostly quiet, thanks to the Gotthard basis tunnel and the more recent car-only pass road. Once you reach about half-way up, you hit the old Tremola road, a cobbled climb with 20+ hairpins that (thankfully) almost never exceeds an ~8% gradient.