At two acres (0.809 hectares), this indoor scale model of the San Francisco Bay and its tributaries is one of the largest in the world. Used by the Army Corps of Engineers for testing the environmental impact of shoreline development, toxic spills and weather conditions, it is open to the public and an impressive sight. A complex hydraulics system pumps water in and out of the model, mimicking the ebb and flow of the actual tides at the Bay Model Visitor Center. For the budding ecologist, oceanographer or civil engineer, there is no better attraction. Who wouldn't be interested in seeing the Bay Area reduced to a scale of 1000 to 1 horizontal feet?