This has got to be one of the sexiest pools that I've ever seen. Located in Singapore atop the three skyscrapers of the Marina Bay Sands hotel, a casino resort, the main feature of the roof is a 500-foot-long pool suspended more than 500 feet in the atmosphere--55 stories to be exact. To make the pool that much more endearing (scary), it's an edgeless pool that gives the impression that you could just swim right off into oblivion. Of course, an edgeless pool doesn't actually work like that, so it's perfectly safe.
The pool itself is part of the greater Sands Skypark, a 1,250-foot-long park that offers lounge chairs, a bar and restaurant, botanical garden and observation deck for relaxing and enjoying the view from the sky. It was designed by Moshe Safde and cost $80 million to build. It's available to guests of the hotel and is offered to public visitors for a fee of $20. Seems like a reasonable price to pay for this beautiful attraction.
You can see a number of additional images on the original DesignBoom post.