This is Lo Gekhar monastery, another AFCP-funded project. Lo Gekhar dates back to the 8th century and is possibly the oldest monastery in Mustang. According to legend, it was founded by Guru Rinpoche, who brought Buddhism from India to Tibet and Nepal (and had to kill demons to build the monastery). The monastery is surrounded by red brick stupas. While modest, Lo Gekhar is incredibly important to Tibetan Buddhism in Nepal.
Next: caves.