The Mountain View Adobe is one of the oldest structures in Santa Clara County, a humble mud-brick building that predates the Gold Rush and the city around it. Built in the 1840s during the Mexican period of California, it served variously as a way-station for travellers on the El Camino Real, a saloon, and a general store before falling into disuse. The building's survival is something of a small miracle given the pace of development around it.
The adobe has been stabilised and is recognised as a local landmark, though it isn't a full-scale museum — more a quiet piece of living archaeology in the middle of a modern suburb. It stands at 1237 Escuela Avenue, not far from downtown. If you're interested in California's pre-American history, it's a ten-minute detour worth making.