That's a variation of the "floating staircase", a popular feature in mid-century modern architecture. Other forms would involve cantilevered steps, their supports imbedded in a wall, one end sticking out into the air.
no hint on country? Whenever I see this stuff I think it must be in Chernobyl or something like that. When I was little, my Dad did odd jobs and one time we had to clear out an abandoned reform school. It was like everyone left with very little notice. Gave the whole place a real creepy feel which was made worse by the cows who were now grazing on the lawns.