It’s hard to believe that millions of people live just a few miles from these places.
That’s exactly right. Some amazing wilderness within just minutes of big cities all over the country. That’s especially so near San Fran, Oakland and San Jose. In San Jose, you can drive up to Ohlone College (actually in Fremont) and head out on a 32 mile backpacking trip to Livermore through some really rugged mountains and back country.
Between, State, County, Local parks, and open spaces, there must be over 1000 miles of trails in the Bay Area. Certainly if you include Monterrey County/Big Sur.
MROSD has about 225 miles of trails, and if you ask me, they don't have as many trails as they should on their property.