A little under five miles of gentle walking, on clearly marked trails helped by the free leaflet at the trailhead.
We followed the volcanic trail, not completely in order, as it led us round the park, educating us about the formations in this part of the East Bay area. The tunnel and freeway are out of sight most of the time.
There were birds of various kinds, from Steller's and other jays, to some so far unidentified by us, small bold black-headed birds, and this one seen on a bush nearby, possibly a female lazuli bunting or a female western bluebird .
Butterflies, white and coloured, large and small, the scent of eucalyptus, pines and in the open areas anise.