Lying on my bed, doing nothing I recently noticed flies usually fly in small circles, right under my ceiling lamp. Worth noting - the lamp was off as it was middle of a day. And those flies kept flying like this for hours, not moving anywhere alse! Later I noticed it repeated every day, pretty much the same pattern. Why is that?
Flies use any object they can find as a landmark.
Source: Jochen Zeil. The territorial flight of male houseflies (Fannia canicularis L.) Behavioral Ecology and Sociobiology. August 1986, Volume 19, Issue 3, pp 213-219