Unterseen is a historic town and a municipality in the Interlaken-Oberhasli administrative district in the canton of Bern in Switzerland. Unterseen literally means Lower Lake, which is correct, since Unterseen is located on the flat area on the eastern shore of Lake Thun between the two creek Lombach below the Chienberg to the north and the Aare to the south, which both flow into Lake Thun. The historic town however is mainly found at the nothern bank of the Aare, which flows here from Lake Brienz to Lake Thun (therefore lower lake). Just accross the Aare is the town of Interlaken. Both municipalities are located on the flat aluvial land among steep mountains, which is also called the Bödeli.