This cover came from USA and depicts 4 stamps, including an old 8c stamp (on the right corner) celebrating the 400th. anniversary of Fortress of San Juan in Puerto Rico.
La Fortaleza and San Juan National Historic Site in Puerto Rico is a World Heritage Site since 1993, located in and near San Juan, Puerto Rico. It comprises a series of fortifications across two properties: La Fortaleza, San Juan National Historic Site, Castillo de San Felipe del Morro, Castillo de San Cristóbal, El Cañuelo and San Juan City Walls. These structures were built between the 15th and 19th centuries to defend the city and harbor of San Juan and are examples of European military architecture adapted to port cities on the American continent. La Fortaleza was the first defensive fortification built for the city. The historic site also includes Castillo de San Felipe del Morro, Castillo de San Cristóbal, El Cañuelo, and three-fourths of the old city wall.
