Best pool: Rosewood, Washington, D.C.
This indoor-outdoor rooftop aquatic complex, which will be reopening in April 2019, is lined with quartz walls and has a fireplace that welcomes you into the enclosed space. Hotel visitors have access to a 24/7 personal assistant who can reserve deck chairs, fetch sunscreen, deliver cocktails and food and even adjust the pool temperature. Once you’ve toweled off, the same helper can book ballet tickets or a shopping trip.