Kerala has the evocative tagline of "God's Own Country". Malaysia is "Truly Asia". England has "Cool Brittania". Mumbai is searching for one such logo..:) Image is everything. A tagline describes the city/country in one line. It should have spice and punch.
Why, of all things, does Chennai have to have the unimaginative logo of "Singara Chennai"? Apart from the feeble attempt at alliteration, no one who looks at Chennai would say it is "singaram". I did rack my brains to think of something. I couldn't come up with anything decent but I am sure there are thousands who can do it....:)