Why do dogs walk in a circle before lying down?

If you start thinking about how uncomfortable must it be to lie on the bare ground without having a cushion you might be able to understand why dogs circle before lying. Yes, what they are doing is trying to make the chosen place to rest the most comfortable possible.

Their ancestors –the wolves- began doing it because they live in the wilderness and have to make sure that there are no strange things –read snakes or spiders that can hurt them while comfortably resting.

But they also used this technique to soften or flatten the place in order to make it as comfortable as possible.