South of Trondheim, the principal city in central Norway, lies Trollheimen, an area consisting of several plateaus and valleys reaching out to the fjords. As you will understand, Trollheimen means "home of the Trolls", just as Jotunheimen is "home of the Giants". This is a tourist name, actually, albeit a very old one, invented in the 1880's.
Maybe the entrance from the west, is the best in this case. Innerdalen is a beloved valley, with a lush vegetation, and surrounded by high mountains. From Innerdalen continue to the north east, and enter the mountains and valleys of Trollheimen. In its center lie Trollheimshytta, Gjevilvasshytta and Jøldalshytta with the most popular hikes around. From here, several mountains can be climbed. Of course, many huts from DNT and the Trondheim mountain organisation are at your disposal.