Hintersee is a 16.4-hectare lake in the municipality of Ramsau in the Berchtesgaden region, about two kilometers west of the village center. It was formed around 3,500 to 4,000 years ago when a rockfall from the Blaueis Valley of the Hochkalter massif, covering an area of ​​75 hectares, dammed the Klausbach stream, which originates at Hirschbichl, and simultaneously created the Zauberwald (Enchanted Forest). To prevent further silting up due to the transported debris, the Klausbach was diverted around 1900 to its overflow, the Sillersbach stream, before finally flowing into the Ramsauer Ache river. Despite this, the lake now only has a third of its original surface area. Today, the lake is fed only by small tributaries from the west and northwest. One of these is the Antonigraben stream, which originates below the Edelweißlahnerkopf mountain and flows into the lake a few meters from the listed Antonikapelle chapel. The lake has a maximum depth of 18 meters and reaches a water temperature of around 16°C in the summer months.