Ayutthaya's main draw is its temples and ruins. The historical park covers the island's core, but notable sites extend beyond it along the rivers. A full day gives you time to see the highlights; two days lets you explore at a pace the place deserves.
Most temple ruins charge a small entrance fee of 50 baht each, or you can buy a combined ticket covering six major sites for 220 baht. The sites are open from 8am to 6pm daily.