Due to this poor feeding, Environmental protection is very important as the lake would suffer long term damage if polluted as the second of the rivers, Rigiaa, feeds only a marginal amount into the lake at its southern end.

Toward the south-west extremity of the lake the Rigi descends rather steeply to the water's edge, while part of its east shore forms a narrow level band at the foot of the 1,583 m (5,194 ft) Rossberg, and the Zugerberg.

The culminating point of the lake's drainage basin is the summit of the Rigi at 1,798 m (5,899 ft).

Many fish (including pike and carp of considerable weights) are taken in the lake, which is especially famous for an endemic kind of trout (Salmo salvelinus, locally called Rolheli).

[2] In the early 20th century, a railway (formerly part of the St. Gotthard main route) ran along its eastern shore past Walchwil to Arth at its south end, which was connected initially by a steam tramway with the Arth-Goldau station of the St. Gotthard line.