If you avoid the cars-only Richmond and Bay Bridges you can run, jog, hike or bike from Napa to Milpitas, from Burlingame to Berkeley on the Bay Trail. 350 of its projected 500 shoreline miles are already in place and from my experience, very well maintained. For most of its length as it passes through restored wetlands it is comfortably flat. The Trail is a remarkable feat of cooperation among the 47 cities and 9 counties it passes through. Enjoy it before the Bay rises and it’s gone.