You know when you come across these hills at Shorebird Park in Foster City you are in a fun place. Finding them is quite simple, just take any dirt path off the main biking trail that heads towards the Bay. One Yelp reviewer warned to watch for snakes.
On a Google map image the path is marked as BMX trail and Bike BMX Jumps. If you look up dirt jumping on Wikipedia you find an image of the Foster City Shells Dirt Jumps.
So, it might not be such an unexpected destination after all. I enjoyed being there without any bikers around. But if you are a BMX biker or love to dirt jump you found heaven. I definitely want to go back and hopefully take some pictures of jumping bikers. The path is dirt mixed with oyster shells. It crushes under your shoes like tightly packed snow.
Do you have any good pictures of dirt jump bikers?