freinds, kannanoor koppam still has the remnants of an old fort. it was initiated by later kings of mediavel cholas. it was used mainly to prevent armies from hoysalas. i do not think thiruvannamalai was ever a capital of medieval cholas. it could have been a stratergic post against invaders from karnataka. even chidambaram was never a capital of cholas.
there were a string of fortresses along the northen bank of kollidam starting from karur,kannanoor, srirangam, lalgudi,pazhuvur, mazhapadi, gkcpuram, kattumannarkoil and chidambaram.
tvmalai,vridhachalam,thirupadiripuliyoor(cuddalore) are important front line defences to the cholamandalam.
i may be inaccurate because i am not a full fledged researcher. gandhi