The Alvord Lake Bridge in San Francisco’s Golden Gate Park is the oldest surviving concrete bridge with metal reinforcing bars in the United States. It was built in 1889 using twisted metal bars, known as Ransome bars, which were patented by Ernest L. Ransome, an early pioneer in reinforced concrete design. The bridge also displays interesting details, such as concrete that was formed to have the appearance of stone and decorative concrete stalactites under the bridge. It is a popular spot for visitors to the park, who come to see its historic significance and enjoy the peaceful surroundings.