It is the diversity that I love about Northern California. Of course, the US is full of great outdoors such as Colorado Rockies, Yellowstone, Utah, Arizona and many others. But the advantage of Northern Cali is that you can enjoy San Francisco: one of the best cities in US and also experience several great outdoors that are easily accessible. This allows you to make the most of your vacation time.
I have visited the area many times and explored quiet a few places. But there are some places in Cali that I don’t mind visiting again and again..:-). Because only a handful of other places in the US offer the same level of experience (I am excluding Hawaii and Alaska). Now the Californians might disagree with me but I have to state the facts..:-)