This climb starts in either Ilanz (694m) or the the east in Reichenau-Tamins (595m). The climb from Ilanz is the shortest and most consistent climb, especially after they built a tunnel on the east side that you have to climb over with your bicycle on a local road, but that climb has a long flattish section through Flims and then going over an unnamed pass at 1113m before a short descent to the turn-off and the hard climb to Nagens.

From the turn-off on the main road in the Surselva it is still a 1083 height metres to the top and this climb is among the hardest climbs in all of the Alps, but it is never extremely steep (always under 20%, max 16.3% over 100m says Michiel, which might mean that it is close to 20% during that stretch). It was not long since it all got asphalted and the road is nice, but it is a hard climb in part since it is rather unevenly steep most of the time. There is even a short flat section that ends with a little bridge and a place to fill up water before the long last hard section.