Underground Russian Submarine Base & Dock
It was a big underground submarine base and docks once in USSR. After the Soviet Union collapsed and Russian army left Ukraine it was partly abandoned and some of its parts was converted into a museum later.
(Thank you for the link, T.W.) More photos available here.
- EDIT: apologies for the nonlinky; fixed now.
Where are our enterprising James Bond Villains now?
Damn – those are cool photos.