The most outstanding structure in the old city is the Alcázar, a palace built for Columbus's son, Diego, and his wife, who was also niece to Ferdinand, king of Spain. Diego became the colony's governor in 1509, and Santo Domingo rose as the hub of Spanish commerce and culture in America. For more than 60 years, this coral limestone structure on the bluffs of the Ozama River was the center of the Spanish court, entertaining such distinguished visitors as Cortés, Ponce de León, and Balboa. The nearly two dozen rooms and open-air loggias are decorated with paintings and period tapestries, as well as 16th-century antiques. A walk downhill from the Alcázar leads to the impressive Puerto de San Diego, which dates from 1571 when it was built as the main gate into Santo Domingo. Some of the original wall can be seen by this gate, which once guarded against attacks coming from the river.