This place was Bulgarian communist party headquarters before communist rule was ended in 1990 under the pressure of street protests. Since then nobody is maintaining the place and it has turned into a ghost building exemplifying the brutalist architectural style common to many state constructed communist buildings.
Local authorities are trying to keep it closed for visitors due to danger of falling objects. But every time they seal a hole, another one is discovered or made by curious tourists and visitors.
I was quite surprised how popular this place is. Inside I met a guy from Malaysia who claimed he traveled the world visiting such places and came to Bulgaria only to visit Buzludzha.
Here is how this place used to look like before the democratic changes:
And how it looks now:
