Glen Cove designer Greg Lanza might have staged this Oyster Bay Cove house. But did he need to? Built in 1993, the 12,000-square-foot Contemporary features a lighted tennis court, an indoor pool with sauna and lots of style. "It's very cool ... very sleek," says co-listing agent Deborah Hauser of Daniel Gale Sotheby's International Realty. Price: $3,999 million.