Unterseen is a municipality in the Interlaken-Oberhasli administrative district in the canton of Bern in Switzerland.Unterseen is located on the Bödeli, between Lake Thun and Lake Brienz, and immediately across the Aare river from the town of Interlaken. Along with Interlaken, Unterseen is an important tourist center in the Bernese Oberland, and from the town one can see the mountains Eiger, Mönch and Jungfrau.