Around lake it was nice but bit boring for riding, but later it was more for riding then for views
The Koppen Pass is on the L547 - L701 between Hallstatt and Bad Aussee and basically runs West / East. Hallstatt itself is a very scenic village on the lake of Hallstatter See which can get very busy during the summer. The Pass a short cut to Bad Aussee but most of the heavy traffic uses the major road around the other side of the lake. It is open most of the year.
Expect traffic approaching Hallstatt from the west during the summer months, including many coaches. It is a nice sweeping road slightly above the lake with plenty of room to overtake or filter. Hallstatt itself is worth a stop and bikes can usually park very close to the village centre. On reaching Hallstatt from the west you will enter a very narrow one way tunnel which takes you around most of the village. Emerging from the other side you will leave the village and follow the shore. Then it is typical Austrian Valley scenery until the start of the Koppen Pass. The pass itself is fast flowing bends with nothing really to catch the inexperienced rider out. There are no habitats along the way and just a couple of small parking areas so Hazards are minimal. The road surface is good for almost all the route but there is a dodgy surface for about 1km as you drop down to Bad Aussee.
See the attached video.