Fortín San Juan de la Cruz (Fort Saint John of the Cross), known locally as El Cañuelo, was built on Isla de Cabras Island at the western end of the entrance to San Juan Bay, in Puerto Rico. The square coastal fort has massive sandstone walls that date back to the 1630s. Although the U.S. Navy bombarded the fort in 1898, the fort survived. Today the fort is part of the San Juan National Historic Site, which is listed as a UNESCO World Heritage Site and on the National Register of Historic Places. One cannot enter the fort, but one may walk around it.