The oldest traces of a settlement in the area are scattered neolithic tools. During the second century AD, a Roman graveyard was built in the area. An Early Middle Ages cemetery shows that there was a settlement in the area and by the High Middle Ages at least three forts had been built in the area. The area was known as "Interlacus" by 1133 when Interlaken Monastery was founded on the opposite side of the Aare. Interlaken village grew up across from the Monastery in the following years. By 1239 it was known as "villa Inderlappen" and in 1280 it was "civitas Inderlappen". The city of Unterseen was founded on 13 July 1279, when King Rudolf I von Habsburg granted Baron Berchtold III of Eschenbach-Oberhofen permission to build a stronghold between the two lakes. The name came from "unter," which in Middle High German meant "between", and "seen," which means "lake." The fortification was given Stadtrecht (town privileges) in this agreement. By 1281 Interlaken and Unterseen was mentioned collectively as "stat ze Inderlappen oder Undersewen" and in 1291 they were called "Inderlappen, genant Undersewen".