Polonnaruwa is not a food destination, but its hotel restaurants do solid Sri Lankan curries and there are roadside places near the new town that are cheaper and just as good. Most travellers stay at one of the lake-front hotels and eat dinner where they sleep — the views over Parakrama Samudra at sunset more than make up for an otherwise unmemorable buffet.
For lunch, try the rice-and-curry places in the bazaar at Kaduruwela, about 4 km east of the ancient city. Look for kottu roti, fried chopped flatbread with vegetables and curry — the Sri Lankan answer to fast food — and buffalo curd with treacle, a north-central speciality. The watermelons of the surrounding dry zone are excellent in season.