What's special about this one is that not only can you walk through the rolling sandstone hills but you can also go underneath them! The whole area started as a coal mine, and used to be the population centre of Contra Costa county. When coal prices collapsed the five towns that were here upped and left - literally. People took their wooden houses apart, loaded them on carts and moved them elsewhere.
Then in the 1930s they started mining sand here to make glass, due to its high silica content. It's the sand mines you can go into now, and $5 gets you an hour-and-a-half guided tour around the giant man-made caverns that were left behind. It seems that much of the population came from South Wales, which makes sense given the mining heritage there, and the cemetery (all that's left of the the five settlements) is full of Joneses, Evanses and Davises. I guess they lost the "e" on the way through Ellis Island.
Save Our State Parks!
This used to be the biggest town - there's the cemetery on the hill.
Mine entrance.
Here's the "black diamond" for which the area is named.
Safety is central to everything that Chevron does.
Into the tunnels.
Unfortunately most of the people on the tour were cub scouts, and not the polite British variety.
The black rock circle bit you can see is actually a fault line. Yep, we walked through a fault! Albeit a dormant one.
Cavernous.
Afterwards we walked up to the graveyard, and spotted some almost familiar names.
