Funtensee is a karst lake on the Steinernes Meer plateau in Berchtesgaden National Park, Bavaria, Germany.

On its shore is the Kärlinger Haus mountain hut which is open for the summer season; in addition, there is a winter room available.

It is theorized that due to the unique situation of trapped cold air, a temperature of −55 °C (−67 °F) is possible.

[3] Temperatures are regularly monitored by a private weather station installed by Jörg Kachelmann.

The exact route the water takes underground has not yet been established, and an extensive cave has not been ruled out, but the outflow point is not accessible to humans for investigation.