One of San Francisco's less well known attractions is Ft. Point National Historic Site. Though you've probably seen it thousands of times as it sits under the southern span of the Golden Gate Bridge. Actually, the chief engineer redesigned construction of the bridge to preserve the fortress. Fort Point was completed just before the Civil War to defend San Francisco Bay against hostile warships, though no military action ever occurred there. Worth the time if you ever visit the Bay Area and of course, take a camera.