Inevitably in the various Top 5 oddest monuments in the world lists, this "flying saucer" construction has sat on top of a Bulgarian mountain since its erection in 1981, when it was designed to celebrate the Communist Party's supposed eternity.
Communism collapsed in 1989, however, and since then the grounded man-made UFO has ran to seed. Neither the heirs to the Communists, nor the Bulgarian state have taken any care of it and the building, or whatever remains of it, is now in severe danger of collapsing. Significantly, the J. Paul Getty Foundation in the United States recently granted funding to survey the monument and possibly conserve it.
Where in Bulgaria are you?