Benicia - Visible across the Carquinez Strait at the north end of the Martinez-Benicia Bridge.
Concord - One of the largest cities in the East Bay, offering a variety of shopping and dining options.
Pleasant Hill - This neighboring town is primarily a typical family suburb, but it does offer options for food and shopping.
Walnut Creek - The downtown Walnut Creek area offers shopping, bars, and restaurants.
Mt. Diablo State Park (http://www.parks.ca.gov/?page_id=517, (http://www.mdia.org/spinf...) - As one of the tallest mountains in the Bay Area, Mt. Diablo dominates the area landscape and provides an escape from the suburbia which surrounds it.
Berkeley - Eclectic, political and always interesting, Berkeley is only a 20 to 25 minute drive away. Alternatively, using BART, either a) transfer at the MacArthur station and exit at Downtown Berkeley, or b) exit at Rockridge and walk ~2 miles to downtown.
San Francisco - Although "the City" feels a world away, it's just a 46 minute BART ride from North Concord/Martinez station to the Embarcadero or a 35 minute to 1.5 hour drive, depending on traffic.
