This is what I want to see in Sri Lanka - their tea plantations. It would be great if I can see how they grow and harvest the tea leaves plus the processing. Maybe the entire process would be fun to watch. From what I understand, tea is the main industry that supports the economy of Sri Lanka that's why Ceylonese tea is the best tea, according to tea lovers. However, I would also appreciate to see some other sights in Sri Lanka particularly those related to their culture.
Sri Lanka is indeed a beautiful country, I have a few friends who have been there and they definitely recommend going there. For details on more places in Sri Lanka, you can visit dedicated Sri Lanka section on the forum.