We discovered the Iron Horse Trail last weekend, and we will definitely be going back! Formally the Southern Pacific Railroad, this now paved trail begins or ends (depending on how you look at it) in Concord. It travels 18 miles through Walnut Creek and ends in Dublin. It's perfect for biking, walking, or jogging. It has little parks along the way to stop and eat lunch. With a four year old and an 8 month old, we probably only did 12 miles round trip on bike, but we will come back to bike another section of the trail soon!