A calm lake lies near the Oberalp Pass. This lake's water flows clear and fresh into the valley. The Tomasee (Lake Toma) is considered to be the source of the Rhine. And it is only here that the river that flows through four countries can still be crossed with a single step.
The idyllic hilly countryside around the lake, the medieval castle of Hallwyl with its heritage exhibitions, and the romantic boat trips round the lake make Lake Hallwil and the nearby Seetal valley a small but popular tourist area.