the part of a building or organization where few people are allowed to go, especially where the most important or secret work is done

His basement laboratory is the sanctum sanctorum to which visitors are not invited. 他位于地下室的实验室是一处私密之所，不接受访客。

Authorities raided the sanctum sanctorum of the cult. 当局突袭了这个邪教的秘密据点。