This is one of the most important elements of Tibetan Buddhist practice: the retreat. Lama practice entails meditation, chanting and practice in a place of isolation. Minimums 3 years, and up to 30 years, are required, with some never leaving the retreat for life. The retreat venues are called retreat caves. As nowadays the retreat is often held in a built-up environment, the older retreat caves have become history. This photograph has therefore become a rare and valuable visual heritage.