There is something essentially pagan about Sukkot. The season is turning from summer to fall; leaves are stirring; there is the smell of overripe vegetation. Sukkot is a biblical holiday, and was one of the pilgrimage festivals to Jerusalem for the blessing of the new fruits. The historical reason for the holiday was that it symbolized the impermanent structures where the Israelites dwelled during their 40 years wanderings. But really, what we have here is an agricultural holiday given a historical dimension (often done in Judaism, and other traditions).
I like the symbolism of the sukkah. It is not permanent. One must be able to see out of the roof. Often, the thing gets knocked down during autumn storms and one is forced to build it again. Everything in nature is slowly fading away. During the waving of the lulav, one turns to all points of the compass, and up and down, to symbolize that no place is devoid of HaShem.
The two symbols dovetail. Nothing is permanent. Everything is in flux. There is only HaShem. We are part of all this and it is all the same. Earth, sky, water, air. Everything is One.