Last updated: February 25, 2021
Place
What is the Rust-Colored Patch on the Tunnel Wall?
Please stop here in front of the tunnel entrance.
As it must be clear by now-building the Point Bonita Lighthouse was a difficult undertaking, as this closed steel door will attest. To go beyond this point without trained Park Rangers is too dangerous and not allowed. This tunnel opens Sundays, and Mondays at 12:30pm and closes promptly at 3:30pm. We recommend that you begin your hike no later than 2:30pm. If you return during these times, you will be able to visit the lighthouse.
As shown in the photograph, before this tunnel was built, there was a walkway called the "gallery," constructed on the left side of this sheer cliff. But constant damage due to unpredictable rock slides necessitated building a safe 118-foot long tunnel. Because of the highly unstable rock, dynamite was not used to create the tunnel; instead workers had to hand dig it. Notice the rust-colored patch above the tunnel entrance. It is a type of green chlorophyte algae known as trentepohlia. Its growth on the rock walls is a testament to the high level of moisture in the air.
There are many geographical areas that, by their unique nature, have had a profound effect on human history; one of these is the Golden Gate. At the outset, the ability to safely navigate or even locate the Golden Gate seemed nearly impossible. But ultimately a robust lighthouse navigational system changed all that and led to the growth of an internationally beloved city. San Francisco is home to an amazing diversity of people many who arrived by sailing through the Golden Gate. Today, the ports of Oakland and San Francisco host many international visitors and conducts significant global maritime trade. All this would be impossible without the hardworking keepers and the lanterns, bells, horns (and cannons) of the Lighthouse Service.
Thank you for taking our cell phone tour of the Point Bonita Lighthouse. This tour was produced by the National Park Service and Antenna Theater.