I couldn't find the entrance, I asked at the balloon store at this address - they don't know, I went up to all the floors, walked around the building, looked into the courtyard, knocked on all the doors and, just in case, went around all the buildings in the area. There were no signs, no options where it was hidden. I wrote a question on Instagram to Yandex. Direct, how to get it - it's been three days already - and they haven't answered. Yeah.