The ancient city is spread across a large area but the main sites are connected by a single road, making it easy to visit by bicycle (available for hire near the entrance).
The Quadrangle is the highlight — a compact group of over six major structures including the beautiful Vatadage, the Hatadage, and the Satmahal Prasada, a distinctive stepped pyramid showing Cambodian influence.
The Gal Vihara, further north, should not be missed. The Archaeological Museum near the entrance provides good context before you start exploring.