Trivandrum is a major transport hub and international airport in southern India, but it doesn't have very much to offer to tourists. The main temple is closed to non-binding and the palace next door is closed to everyone, except the museum.
So we went to Kovalam for the day. There is some debate on which town has the better beaches, Varkala our Kovalam, but I favor Varkala. Despite the pizza-souvenir-massage circus, the views from the cliff promenade make it much more scenic, it has the better beaches, and the Indian food I had is equally terrible in both. Kovalam is quieter, there are few backpackers there.