Buzludzha, Stara Planina Mountains
Buzludzha is one of the most controversial and world-famous communist relics in the country. This UFO-like crumbling monument is perched on a mountain top as if ready to fly off at any moment. It was built as a house-monument of the Bulgarian Communist Party in 1981. One of the most impressive parts inside it were the intricate mosaics inside the main hall telling the story of the party. The monument has been attracting urban explorers from all over the world, which is why 24/7 guards have been sent there recently.