Fort Point is a National Historic Site and part of the the Golden Gate National Recreation Area. It was built between 1853 and 1861 to protect San Francisco during the Civil War. It is the brick building in the bottom picture in the foreground underneath the Golden Gate Bridge.
The fort is open to walk around Friday through Sunday and is free. The entire fort is also a museum hosting a recreation of civil war era life. Climb the granite circular staircases to the roof for spectacular views of the bridge, the bay and the city.
The bridge was specially engineered to save the fort from demolition and is a "must see" stop on my tour of the city.
It was raining during my last visit. Thanks to my sister for suggesting reflection shots in the puddles. I received several correct answers this week. Thanks for playing.