A walk around the Sibley Volcanic loop in the Oakland Hills is a geological trip through magmatic time! Grab a map at the information kiosk in the parking lot and head out for a footnoted hike around the remains of a sheared section of a 10.5 million-years-old volcano. Oakland truly has it all.
The labyrinth at the bottom of the remains of a quarry. Mt. Diablo is visible from this bluff and in the other direction, we saw Mt. Tam in Marin. It was a very clear day.