This is a high-contrast pano. Typically, you would not see a photo like this because it was a brilliant sunny day. If you try to expose this as one shot, the sky will be too bright or the trees/hills will be too dark, etc. There is just too much contrast.
So... this pano consists of two photos, one exposed correctly for the sky and one exposed correctly for the trees, then stitched together and exposure-adjusted.
