There are a lot of trails here with lots of turns. Get a map at a local bike shop otherwise you will likely either get lost or miss the good stuff.
How to get there:
Park at Olympia Stadium (hosted the 1936 Winter Olympics) and head into the mountains. When the road forks about 500 meters past the stadium, turn right and go straight up the mountain on the paved road to Partnachalm, then on to the Partnachklamm.