Tromøya is one of the best migration sites along the outer Skagerrak coast of Aust-Agder county. Tromøya is 12 km long, situated just outside the town of Arendal, connected to the mainland with a bridge. This populated island is covered with mixed forest, with some agricultural areas, such as around Lake Skottjern. Its outer coastline is littered with rounded rocks, just like at Mølen and Jomfruland, clearly showing that Tromøya too is a part of the moraine ridge Raet. A variety of birds can be found here at all times of year. Good places along the coast are Bjellandstrand and Hove.