Wikipedia
In Hinduism, Siddhashrama ( Devanagari:सिद्धाश्रम) is considered as a mystical hermitage, which according to a tradition, is located in a secret land deep in the Himalayas, where great yogis, sadhus, and sages who are siddha's live. This place is also revered as the mystical land of Shambhala by Tibetans. According to another tradition, the Siddhashrama is located in the present-day Buxar district in Bihar. Among the Sadhak of different cults Siddhashram is famous as ‘Siddhalok’, ‘Divyabhumi’, ‘Gyangunj’, ‘Shambala’ etc. Though any Sadhu, Sanyasi, Yeti, Monk and Yogi might have known 'Siddhashram' by any name or various cults might have used different worship or Sadhana methods according to their beliefs. The context of this supernatural land has been mentioned in many ancient scriptures along with four Vedas. The Siddhashram is described as a divine place in spiritual journey. Thus it is also believed that while discharging their divine works in this universe the spiritually empowered Yogis remain in constant touch with Siddhashram and they visit it regularly. Further more, it is also believed that the divine personalities like Ram, Krishna, Buddha, Shankaracharya, and Ma Anandamai etc. are present along with their bodies at Siddhashram.
Siddhashram is considered as the base of spiritual consciousness, heart of divinity and the mortification land of great Rishies. Siddhashram is equally scarce to human beings and all the visible and invisible creatures. Thus, the Siddhashram is assumed as a very scarce divine place. But it will be possible to get the divine power to enter this scarce and sacred place by doing hard works through Sadhana procedure and following Sadhana path. Siddhashram is a secret and mystical land deep in the Himalayas, where great siddha yogis, sadhus, and sages live. Siddhashram is the ashram by our ancestors, saints, sages & Yogis of high order. It is referred to in many Indian epics,the Veda, Upanishads and Puranas including the Rigveda, the oldest scripture of human civilization.
Siddhashram is the society for the enlightened people or siddhas. The person, who reaches high level in sadhana can reach the mystical siddhashram with the blessings of the guru, who is the regular of this place.
The aashram was established by Param Pujya Dada Gurudev Sacchidananda Maharaj. This aashram lies near the Mansarovar lake and the Kailash. Siddha yogis and sanyasis are meditating in this place for thousands of years. Like many mystical places mentioned in different religions this place can't be seen with naked eyes, it's an experience and only through the path of meditation and spiritual awareness we can experience this place.
Many in Hinduism believe that Maharsih Vashishtha, Vishwamitra, Kanad, Pulastya, Atri, Mahayogi Gorakhnath, Srimad Shankaracharya, Bheesma, Kripacharya, can be seen wandering there in physical form and also one can have the privilege of listening to their sermons. Many Siddha yogi, yoginis, Apsara (Angel), saints are found to be meditating in this place. The beautiful flowers in the garden, trees, birds, siddha-yoga lake, meditating saints and many other things of the place cannot be described in words.