The Durmitor route takes you through the Durmitor National Park between Lake Piva, and the town Zabljak.
It is a great continuation to (or from) the Piva route.
If you are coming from Lake Piva, it is easy to miss the turn, as it kind of turns into the mountain. The first section is funny, as a bunch of hairpins carved into the mountain.
There is no light in the tunnels, so watch out, as they are dark.