After reading VA's comments on the post below, it occurred to me that I ought to look up the name of the church and not just the artist. This is the Church of the Saviour on (not in) Spilt Blood. The blood was that of Tsar Alexander II, not that of the Saviour, and the church was built as a memorial to him. It was vandalized during the revolution and after 27 years of restoration opened again in 1997. It hasn't been reconsecrated and functions now as a museum of mosaics. I have to say VA, that if you got to see this, you were really blessed. All this information comes from this Wikipedia article.