Mt. Taikyoku is a large mountain where Taiitsukun and Nyan-Nyan live. According to Taiitsukun, people with evil hearts will only vision the mountain with rock cliffs, nothing more. This happened to Tamahome in OVA 1.
Taiitsukun's palace is located in the middle of Mt. Taikyoku. The palace architecture resembles that of an emperor's palace but is far grander. During Miaka's first visit to Mt. Taikyoku, both Tamahome and her stayed in a bedroom draped with linen where they stayed until they fully recovered from the blood transfusion. In the main part of the palace exists a giant mirror, which allows Taiitskun to view events currently transpiring from each of the four empires including events that have already occurred. during his three years of training under Taiitskun, Chichiri spent his time at the palace.