If you are near San Fransisco, then I would recommend also visiting Muir Woods. Here you can see redwood trees that are centuries old. There was one tree that had been there since 1776 and was one of the smallest ones there!
The trail is gorgeous though, the picture to the left was taken while I was standing on a bridge looking out to the stream. The sun filtered through the trees so gracefully and just gave you this calming feeling while you were there.
While you are there, you have the option of three different trails to take, the smallest trail is about a mile round trip and the longest was around 5 miles. I personally walked the medium length one and found it a really relaxing walk. Chronic texters beware though....there is NO service throughout the trail.
The picture to the right is one of my favorites from that day. That was my attempt to take a full picture of a redwood but as you can see, it did not work out as planned. The craziest thing about walking through here is seeing just how small you are compared to these trees. The diameter of some of these trees are five feet at least! I would definitely say this is a place to stop and see when in California :) Tah and toodles.