After an architectural competition in 1961 to commemorate the founding of the Bulgarian Social Democratic Workers Party, architect Georgi Stoilov revised his designs, separating the saucer-shaped body from the star mounted in a conjoined tower to give it better stability against wind and the risk of earthquakes. I’ve heard from a Bulgarian contact that the entrance to the towers’ stairs and ladders has now (2020) been closed off with a brick wall. In 2015 there were no such impediments.
U R B E X C E N T R A L 