Maybe reading Stuart Kaminsky's Rostnikov mysteries evoked it from my memory, but this morning a picture of the leaning tower of Pisa on a bookmark in a donated book made me think of Tatlin's Tower, the proposed monument to the Third International.
Models survive in Moscow, Paris, London, Stockholm, but apparently not in Berlin, where I saw one in the dusty display window of an empty building in 1978. It is a pity that it was never built.