Welcome to Castillo de San Felipe del Morro Declared a World Heritage elite by the United Nations in 1933. El Morro is Puerto Rico's best known fortress. Spanish troops fortified this 'morro'. which means 'promontory', to keep seaborne enemies out of San Juan. Today this dramatic castle welcomes multitudes of arriving cruise ships and aircraft to the busiest port in the Caribbean. Over two million visitors a year explore theme windswept ramparts and page ways, where the history of 400 years of Spain in Puerto Rico comes alive.