It can be written out in English, Polish, German or which ever language suits the profile manager. :)
I wanted to edit this to add that the absolute correct place name would be in Russian/Cyrillic. I would avoid using Cyrillic only because less than probably .05% of Wikitree users can read it. Until we arrive at a place where we have people who read it fluently, can make corrections or have a moderator/team of people ... avoid it. It won't serve the profile well, because people won't know where the location is.