WASHINGTON (AP) — Joe Biden has spent his first weekend as president at Camp David, the historic retreat for U.S. leaders. It’s been used by every president since Franklin Delano Roosevelt first went there in 1943 as a personal hideaway. It’s also been the site of major diplomatic negotiations and policy discussions throughout history. The camp’s relaxed atmosphere is said to lend itself to the relationship-building that’s so central to diplomacy. Over the years, presidents have made additions to suit their tastes, including adding a heated swimming pool, putting green and basketball court. During his visit this weekend, Biden played Mario Kart with one of his granddaughters.