There’s a place in Sausalito where a day lasts less than 15 minutes, and you can view the entire San Francisco Bay from 10,000 feet up—without leaving the Earth. No, it’s not some strange sci-fi vortex. It’s the only working large-scale indoor hydraulic model of its kind in the world, The Bay Model, operated by the U.S. Army Corps of Engineers.

This one-time scientific research facility is now open to the public at The Bay Model Visitor Center, 2100 Bridgeway, Sausalito. It’s open 9 a.m. to 4 p.m., Tuesdays through Saturdays. Call ahead (415-332-3871) for hours on holidays. Admission is free.

The model is the size of two football fields, representing 1,600 square miles of the San Francisco Bay and San Joaquin Delta, stretching from the Pacific Ocean to 71 miles inland. Standing on a platform overlooking the model, it’s similar to looking down from a plane overlooking the region from 10,000 feet up.

More than 135,000 gallons of water are pumped daily into the model, simulating tides, water flow, sediment movement, and the mixing of fresh and salt waters. Features that affect the water flow are included, including rivers, creeks, sloughs, ship channels, canals, bridges, and large piers.

The Bay Model was built in the mid-50s by the Corps to test a proposal for the construction of two massive dams in the San Francisco Bay, one where the Bay Bridge stands today, and another between Marin County and Richmond.

Called the San Francisco Bay Project, it was also known as the Reber Plan, named for a former theatrical producer, John Reber, who envisioned fresh water lakes, highways and railways running across the dams to link shorelines, and 20,000 acres of new land created by filling in portions of the bay. The plan was eventually abandoned, after tests and simulations using the model showed it would eventually fail.

From 1957 to 2000 the facility was utilized for research; scientists simulated various conditions, including oil spills, major storms, and human activities along the shorelines. It was reopened to the public as an educational center, and is a popular field trip destination. The mission of the visitor center is to educate the public about policy and environmental issues pertaining to the bay and delta region.

Constructed out of 286 5-ton concrete slabs linked together in jigsaw puzzle fashion, the model is controlled by two super computers on site. Every morning the computers are switched on, and water is pumped in over a 20-minute period. The model is drained into a sump tank each afternoon at 4 p.m.

To study conditions that occur over a long period of time, one full day equals only 14.9 minutes, 100 times faster than nature. In those minutes, the Bay Model experiences two high tides and two low tides. More than 250,000 copper tabs are embedded in the concrete, to simulate frictional resistance and create the right tides and currents.

Visit the model on your own using the self-guided tour, or call ahead and arrange an hour and a half ranger-led tour for groups of 10 or more. The visitor center also features interesting speaker programs throughout the year about the region and its history.