Sibley has so much: views of the Bay as well as Mt Diablo and Contra Costa County, labyrinths to get spiritual with, an off-leash policy for dog walkers, trees and shade, and wide open spaces to take in the sun.  Sitting at the top of the ridge, Sibley can be very hot, windy, foggy or cold depending on the season and time of day.  It's not a big park, but a great one to explore.