The Fortaleza Ozama (in Spanish; Ozama Fortress in English) is a sixteenth-century castle built by the Spanish at the entrance to Santo Domingo, Dominican Republic and overlooking the Ozama River. Named after this river, the castle, also referred to as "La Fortaleza" or "The Fortress", is the oldest formal military construction of European origin still standing in America. An impressive architectural structure of medieval style and design, the Tower of Homage (in Spanish: Torre del Homenaje) stands in the center of the grounds. The castle was designed to guard the entrance to the port of Santo Domingo and defend the city from seaborne enemies. Construction began in 1502 and it was completed in 1505. The gate on Calle Damas was originally built in 1608. The castle was well-built enough to serve as a prison until the 1960s. When the prison was closed, the "Fortaleza" was opened to the public. It is located at the end of Las Damas Street.