The Buzludzha Monument.
Here’s another piece of architecture from the other side of the Cold War. The Buzludzha monument sits on top of a mountain in Stara Planina, Bulgaria. Its now abandoned, but was originally built as a symbol of Socialism in Bulgaria after a group of socialist secretly met there in 1891 to form the Socialist movement there.
Its a shame that not a lot of information is available on the thing, as its pretty damn cool. This site has a great write up on it, however its in Romanian, which I have a rough understanding of, but it translates pretty well with google translator.
Another good photo source.