Saint Ana Lake (Romanian: Lacul Sfânta Ana, Hungarian: Szent Anna-tó) is one of the jewel-lakes of Harghita mountains, the only existing crater-lake in Eastern Europe.
Situated in the Eastern Carpathians of Romania, the lake is formed in the crater of an extinct volcano, and is one of Europe's greatest natural wonders. Surrounded on every side by lush green forest, sprouting from rich volcanic soil, the lake is the perfect place to go for a walk a swim or even a row in one of the boats for hire... The lake is round shaped, having 620 meters in length and 460 meters in width. It has an area of 220,000 m², it is situated at an altitude of 950 meters, and has a maximum depth of 7 m. The depth of the like is lowering (in 1870 it was 12 m). The lake water is almost as pure as that of distilled water, but because of its leak in mineral salts, it is not drinkable. You cannot find one living creature in the water, because of the lack of oxygen.
The Mohos Swamp, a swamp where you can find several unusual and rare species of plants and animals on earth, is located 1 km far from the lake. In the Neogen Era, there were two lakes in the crater of the dead volcano, Ciumatul (Hungarian: Csomad). Today Saint Ana lake is the only lake remaining, the other disappeared - got filled up with decaying remains of old trees, dry leaves, etc., and the area turned into a bushy, lightly forested, boggy land, called the Mohos-láp (Engl. Mohos Swamp). The Mohos-láp has a 10-meter-thick peat cover and becomes a very dangerous place, especially after long rainy periods, when the soft peat becomes so marshy that it inevitably sucks down everything heavy.
St. Ana Lake and it's surrounding area is a natural protected reservation. The lake is the sacred place for those living in it's neighborhood, a pilgrimage place for centuries, but the yearly Saint Ana's festival has become more of an artistic tradition than religious. It's first written mention is from 1349.