Gurudongmar Lake, also known as Gurudogmar Lake,66 kms. from Lachen, is one of the highest lakes in the world, located at an altitude of 17,800 ft (5,430 m) in the Indian state o Sikkim. It is a lake which is considered sacred by both Buddhists and Sikhs. The lake is named after Guru Padmasambhava, also known as Guru Rinpoche, founder of Tibetan Buddhism who visited the lake in the 8th century. The lake is not only blessed by Guru Padmasambava but also by Guru Nanak, the spiritual leader of Sikhism while he had passed through this area, and hence regarded as sacred.
A legend related to the frozen condition of the lake is linked to the visit of Guru Padmasambhava to the lake, on his way back from Tibet. When he saw the lake he felt that the lake was worthy of veneration as it represented the divine location of Dorje Nyima or Chhoedten Nyima. As the lake remained frozen most of the year with no possibility of providing for drinking water needs, the people of the area appealed to Padmasambhva to help them. Then the guru agreed to help them and placed his hands on a small part of the lake area which stopped freezing during winter thus facilitating the source of drinking water to the people. Since then the lake has been considered sacred and devotees carry this sacred water in containers.
In another fable traced to the 15th century, Guru Nanak during his journeys had, while on his return from Tibet visited Sikkim had passed through the lake. He was requested by the local people of Gurudongmar village to help them to make the lake a drinking water source as it remained frozen throughout the winter period. Nanak then touched a part of the lake with his stick and from then onward a part of the lake has remained snow free throughout the year. The villagers had also told Nanak that their “virility” had been affected by the high altitude. Nanak. therefore, blessed the lake and told the villagers that “whoever takes the water of this lake will gain virility and strength”. Since then both the lake and the surrounding hills came to be known as Gurudongmar.
Source : Wikipedia.