This is the core of historic Ayutthaya. A must see. For the best experience, I suggest coming in the morning, before the heat sets in and the arrival of buses with Chinese tourists. There are lots of them.... You can walk around the ruins close to the entrance that includes Wat Mahathat with the Buddha head in the tree. The park is much larger and I wanted to walk it all, but as of april 2019 there was a lot of construction work on the grounds. Looked like they were landscaping so we left that for our next visit. You can hire a tuk tuk at the entrance to take you to see all the sights, or you can rent a bike nearby and leave it at the park entrance when you are finished. Ask in the ticket counter for directions