Ciomatu Massif, is part of the Eastern Carpathians, being at the south – eastern end of the volcanic mountain chain that stretches from the Ukrainian border.
It’s situated in the eastern part of Transylvania, separated by the central part of the province by Harghita Mountains. To the north Ciuc, to the east Nemira and to the south Bodoc mountains are in its proximity. The western slopes end in Olt river defile, where Baile Tusnad spa developed.
The highest point in reached in Ciomatu Mare Peak, at 1301m. Not far the traces of a Dacian fortress can be seen. Now its slopes are covered with pine forests.
On Ciomatu we find volcanic conglomerates and sedimentary rocks.
In the crater of the dead volcano, at an altitude of 950 meters, lies Saint Anna Lake. In the prehistoric ages, there were other lakes in the crater, which, by now, got filled with decaying remains of old trees, dry leaves, etc., and the area turned into a bushy, lightly forested, boggy land, called Mlastina Mohos (Mohos Swamp). Mohos Swamp is covered by a 10-meter-thick peat layer and became a very dangerous place, especially after long rainy periods, when the soft peat becomes so marshy that it inevitably sucks down everything heavy.
The lake is surrounded by legends, mysteries and miracles. Even the shape of the lake is not usual; it looks like a large tear-drop. The lake is not fed by any brook or stream, the only water supply is the rain, therefore, the waters of the lake is nearly as pure as distilled water. The area of the lake was not only believed to be a hiding place for pagan gods or genies, but also has been and still is one of the most adored and respected sacred place for the Christian Székelys, who always come here with a spirit filled with piety.
The area is also a reservation and protected area, with access restriction for environmentally dangerous activities.