It is really an accomplishment of the US Army Corps of Engineers: The Bay Model in Sausalito is as large as two football fields. If you are like me this sounds big, but you only get the real idea of how big this actually is once you stand in the viewing area and you are trying to grasp the entirety.
The Bay Model was built in 1957 to simulate salt-water intrusion, changes to tidal flows, and even movement of pollution. Nowadays the computer models have taken over and this is an educational facility. The US Army Corps of Engineers still operates the facility and offers educational programs and tours.
On my recent visit I was greeted by a ranger. Before I got my map and self-guided tour brochure she gave me a run-down on the model. Going first up a ramp I choose the outside lookout to see kayakers leaving the marina. When you enter the exhibit there are historic facts and explanations of the Bay. Did you know that the gold diggers used hydraulic mining? The run-off was full of sediments and made the Bay rise by more than 10 feet, causing muddy floods! 
The next stop was a short movie, conveniently translated in four other languages besides english. After the movie, be prepared to be blown away. As I mentioned earlier, the scale is massive! Every 14.9 minutes a 24 hour tidal cycle gets recreated. Some of the educational devices are closed off due to COVID restrictions.
Have you walked around the Bay?
The Bay Model Visitor Center is located at 2100 Bridgeway in Sausalito. Admission is free. Opening hours are Tuesday through Friday, 9 am – 4 pm and Saturday, 10 am – 5 pm.