El Faro de Punta Mulas, Vieques

Built by the Spanish between 1895 and 1896, the lighthouse at Punta Mulas crowns a modest promontory at the eastern edge of Isabel Segunda — the first thing you see arriving by ferry. Its lantern room sits 68 feet above sea level; in its earliest days, the fixed red light was visible eight miles out. Automated in 1949, restored in 1992, damaged by storms, repainted in 2014 — the place has had a rough go. Check before you visit: it's rarely open.