All that’s left of William Belden’s Gilded Age resort is a row of rotting wooden pilings jutting from the water off City Island. Belden had conspired with Jay Gould and Jim Fisk to corner the gold market in the 1869 Black Friday panic; disgraced but still rich, he bought the point in 1885 and built a summer playground for the era’s tycoons. Today it’s a quiet, bench-lined seating area.