Since San Jose came up, there is an interesting hitorical site about 30 minutes south of
the city, in New Almaden: the site of the New Almaden mercury mine, now a park
with a small museum. Some wildlife, perhaps, but great old mine buildings and
trails--mostly up and down hills. The mining started in Spanish colonial days
and continued until after 1927, to a maximum depth of 1800 ft. Miners encountered
flooding, boiling geothermal water and CO2 gas.
http://www.newalmaden.org/AQSPark/newalmmus.htmlOn the subject of mining: Black Diamond Mines Regional Preserve in Antioch
(near the Sacremento Delta) has got to be the most unusual preserve in the country
the visitor's center is 200 ft underground! It's located in an old sand mine that once
fed the Hazel-Atlas glass works in Oakland. Mine tours cost $5/person and are
offered on weekends March - Novermber. Surrounding it are numerous coal mines
hand-dug by Cornish miners beginning in the 1860s. The entire area is rolling hills
with scattered oaks and good views of Mt. Diablo. (Other than the Black Diamond
preserve, Antioch is a place to avoid: high crime.)
https://www.ebparks.org/parks/black_diamond/This site lists 5 historic gold mines in California with surface tours:
https://sacramentokids.net/2012/02/22/five-historic-sierra-gold-mines-worth-a-visit/1. Marshall Gold Discovery SHP & Sutter’s Mill -- Hwy 49 between Placerville & Auburn
The spot where the Gold Rush began.
2. Columbia State Historic Park -- Columbia, CA
3. Empire Gold Mine -- Grass Valley, CA
4.Gold Bug Mine -- Hangtown. CA
5. Kennedy Gold Mine -- Jackson. CA
367 miles of abandoned and flooded tunnels.