Looks like a restroom from an old skating rink from the 1970s. They put an uphill slope to the urinals. You'd be peeing and start rolling backward. That place smelled of urine. I hope the owner regretted that decision every day he owned it.
I don't want this to be real, but I know it is because of the pixels.
If digging the hill to set a foundation was too much work, I'd hate to know what the rest of the building (and plumbing and electrical) looks like. But who am I to judge without knowing the situatuon... maybe it was a mountain made of diamond.
I think such a toilet is quite possible. Apparently this is a basement room in which the floor was made of earth. It’s just that those who made the toilet didn’t bother to fill the hole before concreting it.