I do not think many, if any actually for them back. The ones that were not in ruins have long since been converted to other useful purposes- hospitals, old folks homes, government agencies, childcare and orphanages, museums etc. It would take a fortune to restore and maintan these for private usage. Some surplus has been sold, but only the Russian mega-rich or corporate hotel chains can afford them and the work involved. I have read some people have petioned for their old family property, but unless they are Russian citizens, they are not eligible. and, when they saw what they would have to deal with, dropped the idea. Moscow is slightly different, as foreign embassies have leased a few for long term, as residencies. There is a lot more to this, technically and legally but this should get you off to a start.