On the former Mare Island Naval Base in Vallejo is a lush and old fashioned-looking circular park, centered around a quaint, 19th-century bandstand—that, and a 28-foot intercontinental ballistic missile launched from a Cold War-era nuclear-powered submarine.

Taking a closer look, Alden Park is surprisingly unique in more than one way. It is at once—and rather incongruously—a slightly mournful celebration of forgotten firepower and a lovely place to have a picnic (if somewhat disheveled since the US Navy moved out of the large base in the 1990s).

The strangest attraction, the Polaris missile, used to be deployed and maintained from Mare Island. It was in service with U.S. and U.K. submarines from 1960 to 1975, and had a range of 1,000 nautical miles with a 600-kiloton nuclear warhead.

And aside from the now slightly rusting shell of the giant missile, the park displays an assortment of naval weaponry from the last 200 years. Dotted around the edge of the park are the body of a U.S. nuclear-tipped anti-submarine missile, Civil War-era torpedoes and cannons, and a German World War II submarine. There are also a few monuments to military units and who were based at Mare Island during the wars.

Stranger still, all this vintage weaponry is backdropped by a verdant variety of plants and trees from all over the world. They were planted in the 1860s, thanks to Navy commander James Alden, who the park was named after. The green-thumbed commander began encouraging his captains to bring back trees from their excursions overseas. Thanks to this project, there are now elm, apple, bay, olive, apricot, locust, fig, and eucalyptus trees all growing on the curious California island.