#1 of 3: The old spillway of Chabot Reservoir emerges from its tunnel here. The arch--washed out in the sunlight--has the names of the trustees of the Contra Costa Water Company engraved on it. This whole structure is fenced off on one side, but a bit of scrambling will get you here. Lots of poison oak guards the structure. It's still in good shape, but the reservoir has a different spillway now.