This is the Jellyfish House, a home in Marbella, Spain designed by Weil Arets Architects. The owners wanted to have a view of the nearby Mediterranean Sea, which is blocked on the ground floor by hills.
The architects responded by building the pool on the roof of the four story house. Residents and guests who are on the floor below the pool don't have a view of the sea, but they can look straight up the glass ceiling to look at people in the pool.