Cross of Burgundy
During World War II the United States Army added a massive concrete bunker to the top of El Morro to serve as a Harbor Defense Fire Control Station to direct a network of coastal artillery sites, and to keep watch for German submarines which were ravaging shipping in the Caribbean. A lighthouse, rebuilt by the U.S. Army in 1906–08 is the tallest point on El Morro, standing 180 feet (55 m) above sea level. Flagpoles on El Morro today customarily fly the United States flag, the Puerto Rican flag and the Cross of Burgundy flag, also known in Spanish as las Aspas de Borgoña, a standard which was widely used by Spanish armies around the world from 1506 to 1785.