Cathedral of Christ the Savior, Moscow. Originally built in 1881, razed on Stalin's orders in 1931, rebuilt after Communism fell.
Unfortunately a few steps away from Christ the Saviour cathedral remains Lenin’s embalmed body on open display - smack in the center of Red Square.
And even more unfortunately, because enough ‘collusion’ was the rule between key Orthodox church leaders (the ones who didn’t end up in the Gulag) and Stalinists/KGB during Soviet times - the legacy still remains. A lot of ex KGB members merely switched their badges for crosses and church garb. Not *all* are like that, but enough...
Hence why Ukrainian Christians broke from the Moscow patriarchate this year.