Anuradhapura

Anuradhapura was Sri Lanka's capital for over a thousand years, and the ruins are spread out enough that a bicycle is genuinely the best way to see them — the sacred Bo tree grown from a cutting of the original in India, the huge white dagobas of Ruwanwelisaya and Jetavanaramaya, ancient monasteries and reservoirs still in use today. It gets far fewer visitors than Sigiriya, and I find it the more moving of the two ancient cities for exactly that reason. A full day here is worth it if you have the time.