Alvord Lake Bridge, Road bridge in Golden Gate Park, San Francisco, US.

Alvord Lake Bridge is a single reinforced concrete arch, 64 feet wide with a 20-foot span, that carries Kezar Drive over a pedestrian walkway near Alvord Lake in Golden Gate Park. Its face is scored and hammered to resemble sandstone, and the underpass interior has sculpted concrete stalactites.

Built in 1889 by engineer Ernest L. Ransome using his patented cold-twisted square steel reinforcement bars, it became the first reinforced concrete bridge in America. This structure set a new standard for bridge construction and demonstrated the viability of the material.

The bridge takes its name from Alvord Lake, the small lake it arches beside near the park's eastern edge at Stanyan Street. Visitors entering from the Haight Ashbury district pass beneath Kezar Drive through the underpass, where the sculpted concrete stalactites give the crossing a cave-like look.

The best way to experience this is by walking through on foot on the pedestrian path beneath the arch, especially when sunlight reveals the interior details. Access is straightforward and free, making it an easy detour when moving between the neighborhood and the park.

The interior was intentionally designed to resemble a cave with artificial stalactites evoking natural karst formations, despite being constructed entirely of concrete. This unusual design choice was remarkable for infrastructure of the 19th century.