This charming 7 square-block historic district in San Juan is reminiscent of the Spanish Empire. The area was once enclosed by a wall erected by the Spanish with slave labor. The wall was able to hold off attackers that came from all over the Caribbean and beyond. During the 19th century, Old San Juan had become a residential and commercial district. Today, it's the setting for 400 buildings of restaurants and shops all filled with Spanish colonial architecture and under constant restoration. Old San Juan lies on the western end of an inlet, encircled by water; on the north is the Atlantic Ocean and on the south and west is the calm waters of San Juan Bay. A bridge, Ponte San Antonio, connects the old town with the rest of San Juan. The ramparts and old spanish fortresses that once held this town form the outer walls to the bridge. In 1950, Old San Juan was designated as a U.S. National Historic Zone.