Fictional establishment from the television series Space: 1999. The series, created in 1975, assumed (wrongly) that the space program would not slow to a crawl the way it has, and that a full-fledged city on the Moon would be not only possible but well-established by 1999.
Despite Space: 1999's many problems, the concept of the Moonbase was extraordinarily well visualized. The producers successfully created an environment that still holds up as credible today.
The pity of it, of course, is that we don't actually have a base on the Moon, nor any clear plans to establish one.