The Det-Sen Monastery was a place of Buddhist worship located in Tibet. It was named after the second Dharma King, Trisong Detsen. (PROSE: Night of the Intelligence)
The Doctor visited the monastery on at least two occasions.
In 1630, the First Doctor helped the Det-Sen monks fend off bandit attacks and was entrusted with the monastery's holy Ghanta. (TV: The Abominable Snowmen, PROSE: Night of the Intelligence)
In 1735, Abbot Padmasambhava, under the influence of the Great Intelligence, enlisted a local toymaker, Jemba-Wa to begin constructing robot Yeti. (PROSE: Times Squared)
In 1935, the Second Doctor returned to the Monastery, bringing with him Jamie McCrimmon and Victoria Waterfield. They helped the monks and Professor Edward Travers defeat the Intelligence and the Yeti. (TV: The Abominable Snowmen)
In 1980 (fifteen years ago; fifteen years before the September 1995 setting of the main story) or 1984, Victoria returned to the Det-Sen Monastery, which was suddenly destroyed in an explosion caused by the Intelligence. (HOMEVID: Downtime, PROSE: Downtime)