By Christopher Hall

Think it takes hours to circle the Bay Area? Not at the San Francisco Bay and Delta Model in Sausalito. The U.S. Army Corps of Engineers built the 1.5-acre mock-up in the 1950s to test a plan to dam the bay, using 180,000 gallons of water to mimic local tides and currents. The idea died, and for years the model served instead to study oil spills, bay fills, and dredging. From an overlook you can contemplate what you'd see from 12,000 feet up: 300 square miles of bay, ocean, and land. Down on the floor, you can watch as the "tides" change every 3.8 minutes. Ecology and history exhibits include a replica of a Pomo reed boat, while the foghorns and seabirds on an optional audio tour let you imagine you're sitting on the dock of the bay. Information: (415) 332-3870, http://www.spn.usace.army.mil/bmvc.