The Greenbelt Alliance has an interesting hike coming up on Saturday, Oct. 20:

Rocky Ridge Ramble

East Bay – Greenbelt Outing

See what Contra Costa County would look like without its suburban sprawl. This rigorous hike takes us through some of the East Bay’s most pristine watershed, including long abandoned ranches and orchards.
10 am-6:15 pm

More details here. It’s a 12-miler with 2,000 feet of elevation gain. Because that’s how far/high you have to walk to get beyond the suburban sprawl of Contra Costa County. Click on this map to see where the hike starts out from — looks like challenging terrain indeed. The alliance’s event’s calendar is here.