Red Lake (also known as Lake Ghilcoş) is a natural dam lake formed following the collapse of a slope due to the earthquake of January 23, 1838 at 18:45, 6.9 magnitude, VIII intensity, at the foot of Hasmasul Mare Mountain, near the Bicaz Gorge, at a distance of 26 km from Gheorgheni, in Harghita County. At the last measurements, made in 1987, its dimensions are: the lake lies on a perimeter of 2,830 m, the area is 114.676 m² and the volume of water that accumulates is 587.503 m³. The lake was formed at an altitude of 983 m, in a depression with a predominant subalpine climate.
The Red Lake is located between Suhardul Mic, Suhardul Mare on the north side, Southwest Podu Calului Mountains, Licaș Mountains and Kis-Havas Mountains in the northwest, Csíki-Bükk in the north-east and Muntele Ucigaș (The Killer Mount) in the eastern part. The lake is powered by four large streams and 12 temporary water courses, of which the most important are Verescheul (The Red), Licaş, Suhardul, Ucigașul(The Killer).
The surroundings of the lake have a pleasant microclimate, particularly beneficial for the treatment of physical and mental exhaustion, insomnia, neurasthenia. The average multiannual temperature is 8°C, above the 6°C average of the intramontane depressions. The valley is virtually free of winds, very clean air rich in natural aerosols, scenic surroundings provide excellent conditions for those who are seeking for sources of rapid regeneration naturally. Since the 1900s, it has been the recreational spa tourism that has brought development to the tourist services of this area.