Western Hills, Occidental.
I had been wanting to visit Western Hills in Occidental for quite a while. Kind of silly, because I only live 10 minutes away. I finally visited today (only open on Saturday, except tours) and it exceeded every expectation I had. I am so glad that this horticultural mecca is finally reopened, and if you are ever in this part of NorCal, I highly recommend visiting. I posted some pictures on Flickr, but I have to warn you, I missed a lot of plants because there was just so much to see! Everything there was megasized, Cordylines were upwards of 40ft!
Here is a link that might be useful: Western Hills Set