Buzludzha

They lowered a mountain by nine metres with TNT to build this.

The Monument House of the Bulgarian Communist Party, universally called the Buzludzha Monument, sits on Buzludzha Peak in central Bulgaria. Construction began on 23 January 1974 under the architect Georgi Stoilov, a former mayor of Sofia and a co-founder of the Union of Architects in Bulgaria. To make a stable foundation the peak was levelled with explosives, taking the mountain from 1,441 metres down to 1,432 and removing over 15,000 cubic metres of rock. It cost 14,186,000 leva, equivalent to about 35 million US dollars in 2020 terms, and was inaugurated in 1981.

It commemorates 1891, when a group of socialists led by Dimitar Blagoev assembled secretly in this area to form an organised socialist movement. That became the Bulgarian Social Democratic Party, forerunner of the Bulgarian Communist Party, itself the forerunner of today's Bulgarian Socialist Party.

The building is the clearest surviving example of the futurist architecture that communist states built: a concrete disc on a ridge, with a tower beside it, visible for miles.

All maintenance stopped when communism fell in 1989. The structure weakened, and it remains closed to the public because entering it is genuinely hazardous. Do not treat photographs of the interior as an invitation.

It is not abandoned in the sense of forgotten. The Buzludzha Project has begun preservation work with the eventual aim of an interpretation centre for Bulgarian history, and the monument appears on the Getty Foundation's list of Keeping It Modern grants, awarded through the German national committee of ICOMOS, for the immediate stabilisation of its interior artwork. The mosaics inside are the reason people are fighting for it.