Trading convenience and action for comfort and solitude, Novak Djokovic usually avoids Manhattan during his annual romps through the U.S. Open. Instead, he stays at the hillside New Jersey estate of the tech-obsessed tennis coach Gordon Uehling, a longtime friend. The grounds include various courts that simulate the sport’s grandest venues—Wimbledon’s Centre Court, Court Philippe-Chatrier at the French Open and Arthur Ashe Stadium in New York—down to the exact same surface specifications and speeds. There are also pools, space-age recovery rooms and acres upon acres of wooded land. Three days before the 2021 U.S. Open began, Djokovic hiked the grounds.