The Baker–Barry Tunnel connects the former military bases Fort Barry and Fort Baker in the Marin Headlands of Marin County, California. The bases are now part of the Golden Gate National Recreation Area. The tunnel is also known as the Bunker Road Tunnel for the road that runs through it, or as the Five-Minute Tunnel because it is only wide enough to accommodate a single reversible lane, opened to traffic at either end for five minute intervals.