Trölladyngja (troll-mountain) is a volcano just north of Nupshlidarhals on the Reykjanes peninsula, near the international airport in Keflavik and the capital city area.

The mountain reaches a height of 275 metres (900 ft) above sea level, and its sister mountain Grænadyngja reaches 393 meters (1289 ft). The two are quite popular for hiking, since their modest stature makes for a relatively easy climb, and the flatness of the surrounding area makes for a fantastic view.

Trölladyngja is geologically very interesting, as you can see in the unusual colours on its southern side. It is located in a geothermal area roughly four kilometres east of mount Keilir.

The countless other things in the area include whale watching, exploring famous volcanic sites, horseback riding, as well as all of the restaurants and shopping in the capital and surrounding towns.