Sandy Point Farm in Portsmouth, Rhode Island.Concierge AuctionsSandy Point Farm was built in 1902 for Reginald Claypoole Vanderbilt in Portsmouth, Rhode Island.His father, Cornelius Vanderbilt II, built the Breakers mansion in Newport.Sandy Point Farm, now listed for $3.5 million, has 24 stables and a 15,000-square-foot riding arena.Rhode Island is full of architectural marvels from the Gilded Age, but these historic properties rarely hit the market.That's what makes Sandy Point Farm, a 1902 equestrian estate that belonged to a Vanderbilt heir, a rare find.Sotheby's Concierge Auctions is listing the 6-acre property for $3.5 million.