The Fuerte de San Diego is built of stone in the form of an irregular pentagon with five bastions linked by walls. This fort was built in colonial times to protect the port of Acapulco from pirates as it became the most important point in the Pacific for trade with the East, being the primary departure and return point for the Manilla Trade of China and the seat of the Parian market, where highly valued products were traded, through the New Spain, to Europe. The design and construction of the fortress was completed in 1617. It received the name of San Diego, in honor of the patron saint of the Viceroy, and the bastions received the names of the king, prince, duke, marquis and Guadalcázar. It is the most important historical site in the city of Acapulco and the most significant maritime fortress throughout the Pacific. Inside the star-shaped structure is the Acapulco Historical Museum. It also has an auditorium, educational services, guided tours and gift shop. It is open Tuesday thru Sunday from 9:30 am to 6:30 pm. It is located downtown on Hornos street.