The Devil’s Slide Bunkers on the coast of San Mateo County, California. The abandoned military triangulation bunkers.
It was the location of a military triangulation station and observation site used during WWII as part of the Harbor Defense of San Francisco. Through this system they would be able to tell the coordinates of a vessel out in sea because radar had yet to be available.
The bunker was also featured in the 1960 thriller ‘Portrait in Black’ where the main characters pushed a car off the cliff. The car was retrieved from the bottom of the cliff once filming was completed. The Tom Lantos Tunnel just opened in March of 2013 to help bypass the sometimes treacherous path of the Devil’s Slide.
Check out this bunker with these coordinates 37.568116,-122.516418.
Images found Here.