How can a 50-ton gun simply disappear? Learn this and other factoids while helping load and aim the last operational gun of its kind. Photos of the century-old Endicott system batteries in action are on display in an underground cartridge room.

In case of rain, call (415) 561-4323 for schedule.

Located in the Presidio at Battery Chamberlin, north end of the Baker Beach parking lot.

Open 11 am to 3 pm, first full weekend of each month.

Sponsored by the National Park Service.