Must See in Chennai

I'm here for 2 months for work, and so far I've only seen the small area between the office and my hotel. I want to know what are the absolute must sees in Chennai or close by that I will not want to miss while I'm here... I'm interested in seeing temples, architecture, natural beauty, markets or bazaars, or anything else generally exciting. I'm not sure if I'll have access to a car, so it should be close enough to take a cab.