The French still use the Maginot Line, at least part of it. Ouvrage Hochwald is a hardened command center for Drachebronn Air Base.
The French actually re-manned the line after World War II — an event in which it infamously failed — and used it as originally intended until the 1960s when they developed an independent nuclear deterrent.
One of the forts was used as the set for SPECTRE headquarters in the James Bond film On Her Majesty’s Secret Service.