People toast and taste wine on the veranda at the Vino Godfather winery on Mare Island in Vallejo, California. [Photo/Agencies]

Housed in an old Navy brig, this winery is one of several set on Treasure Island, an artificial island in the San Francisco Bay built for the 1939 Golden Gate International Exposition World's Fair. Taken over by the Navy in 1941, the island hosted strategic command and communications center headquarters and remained a military installation until 1997. It was sold to the city of San Francisco in 2007 and is now home to about 2,000 people.

Fat Grape, which makes only red wines and does not add sulfites, a preservative, offers free tastings and is open Thursday-Saturday from 11 am to 6 pm (It's a small operation, so you may want to call ahead to check that it's open before you go: 415-613-8925.) Also on the island: Treasure Island Wines, a collective, and The Winery SF.

Go here for more details on island wineries, http://sftreasureisland.org/Island-wineries.

You can get to Treasure Island by car via the Bay Bridge, or take the MUNI 25-Treasure Island bus from San Francisco.