That is unusual to see such two-story pavilion, but I can imagine why the ancient architects decided to do so being on such height it is a breathtaking view and only possible to enjoy it you need to be higher then trees.
I love such massive wooden pillars. The picture taken from the second story, I can imagine that everyone probably have had a thought of having such a nice terrace where they could enjoy to sit and have a cup of tea or coffee overlooking the nature at the feet and may be feeling himself as a emperor :)