According to the people who designed and built it, 1,700,000 cubic metres of soil were dug out in 1978-1981 in order to accommodate it, obliterating several neighbourhoods.
The concrete poured into it was about 335,000 cubic metres, and the steel used for its construction outweighed the Eiffel Tower. It was inaugurated in 1981 for a major Communist Party congress and would bear the name of Lyudmila Zhivkova, who was the daughter of guess who. In 1990 its name was slightly amended to reflect new political realities.
The huge building, variably described as the best convention centre in the world and an epitome of the late 20th Century urban nightmare, is still in existence and in use today.
The picture here shows Bulgarian actress Rositsa Bradinova-Petrov posing in front of the building a few weeks after its official opening.
Where in Bulgaria are you?