The Dasparkhotel in Germany doesn't have rooms, per se. Instead, it has repurposed sewer pipes that are outfitted with a bed for your sleeping comfort.
Each pipe acts as a standalone room in a park, featuring a double bed, a small storage space and a light. I guess you'll be looking elsewhere for such luxuries as a toilet, a sink and a shower, but nobody said sleeping in a sewer pipe would be luxurious. But hey, it's a unique experience, right?
And don't worry, I'm sure these things have been properly cleaned out before beginning their new lives as abodes.