Waldo tunnel

Waldo Tunnel is the unofficial name of the tunnel taking U.S. Highway 101 from just north of the Golden Gate Bridge into Sausalito. It is named after Waldo Point along Richardson Bay between Sausalito and Mill Valley. This in turn is named after William Waldo, who ran unsuccessfully as a Whig candidate for governor of California in 1853 and went on to found Waldo, Oregon.

The first bore of the tunnel was built in 1937 and the second in 1954. The archways at the ends of the bores were painted in rainbows by the late Caltrans employee Robert Halligan, and for this reason the tunnel is occasionally referred to as the "Rainbow Tunnel". The tunnel features in the Clint Eastwood film Dirty Harry, the Humphrey Bogart film Dark Passage, and in any number of morning traffic reports. The honking of horns in the tunnel, often done deliberately for the sake of hearing the echoes, was the inspiration for harmonicist Bruce "Creeper" Kurnow's composition Honk If You Love Harmonica.

As San Francisco and the Golden Gate Bridge are hidden from the northern approach of Route 101 by hills, it is likely that some portion of visitors receive their first view of the city and the bridge on exiting the tunnel's southbound bore.