This is probably the first differentiating thing that one would find, when one visits Chennai (erstwhile Madras). Kolam (or rangoli as it is referred to in North India). Rangoli in the north, is more done during festivities. In South, and more predominantly in Tamil nadu, it is a daily ritual. The entrance to houses are decorated with a kolam every day in the morning.
(Pardon the bad quality photograph – I have now realized that if I zoom in using my cell phone camera, the images always turn out bad.)