Ayutthaya is about 60 km north of Bangkok. It was the capital of the Thai people before Bangkok from 1351 to 1767 and thus contains an enormous number of ruined temples and buildings from that time. It's an easy trip to get to Ayutthaya from Bangkok. We went via train which took about 2 hours. The train station is just outside the city proper but it's a quick and easy tuk-tuk ride to just about anywhere.
Central Ayutthaya is surrounded by a moat which is actually the Chao Phraya river. A canal was dug so the river makes a rough rectangle and the city is effectively on an island. The central part of the island is the Ayutthaya Historical Park which is an enormous area full of a few major ruins (with admission fees) and a whole selection of smaller (free) buildings scattered around. There are also ruins randomly throughout town and outside the moat as well.
Apparently many people day-trip to Ayutthaya from Bangkok. We spent the night in the city and would recommend it. It's a manageable size (especially after Bangkok!) It's relatively quiet at night. On our first day in town we hired a tuk-tuk to shuttle us around the major sites, generally avoiding those in the middle of the town (that we could walk to the following day). This is Wat Yai Chai Mongkhon, located off the island, not far from the train station. You can climb up the central tower (the gold wrapped one) for a great view of the area.
There seems to be some confusion on the internet at large about reclining buddhas in the Ayutthaya area, at least from what we found trying to figure out what was located where. First, there is more than one. We saw two, but we probably saw less than half of all the ruins in the area. This one, commonly wrapped in gold, is at Yai Chai Mongkhon.
There are also a huge number of seated buddhas surrounding the central temple. This wat was started in the 1300s and expanded in the 1500s. Ayutthaya was destroyed by Burmese forces in the second Burmese war and most of the buddhas located around Ayutthaya were beheaded. These are thus likely restored although we didn't see any information specifically on them.
Next stop was Wat Mahathat which is in the central park area. There is a nominal admission fee here and a small market of food and craft stalls between the parking area and the entrance. That was only true at a handful of sites that also happened to be the ones frequented by tour buses. There isn't all that much to say about this other than it was built in the late 1300s and like all of the wats, it was a temple.
The ruins are impressive and worth exploring but really most people come to Mahathat to see this. It's the head of one of the buddhas which has been wrapped in the roots of a fig tree over time. It's quite possible everyone who comes to Ayutthaya has this picture, certainly there was a line of people taking selfies with it.
If you look carefully there is a line of headless buddha statues on either side of the central buddha in this picture. That is how most of the statues in Ayutthaya look. A few have been restored and perhaps even fewer somehow escaped the original destruction.
Wat Lokaya Sutharam (no admission charge) is the site of the other reclining Buddha that we saw. This one is sometimes wrapped in gold leaf and sometimes not. Either way, it's definitely separate from the earlier picture. It's on the west side of the island down a series of alleyways that don't seem like they should lead to a major tourist attraction. We didn't explore the wat itself here very much.
This is Wat Chai Wattanaram. It's one of the more impressive sites. It sits right on the river / moat outside the island in the southwest corner. It can be visited by boat as well. This is the most Angkor-like temple in Ayutthaya featuring the nine tower architecture. We visited at sunset and it was extremely photogenic. There were also bats coming in and out of many of the towers. The towers here are not stable enough to be climbed. There is a small admission fee here as well.
That ended our first day in Ayutthaya so in the evening we walked out to the closest night market. This one is in a small parking lot just east of the historical park. There are maybe a dozen different stalls. We chose one basically at random, other people were eating hotpot (sometimes called BBQ) and it looked interesting. We're glad we chose this one because they had tables under an awning and there was an impressive rain storm during the middle of the dinner rush. Hot pot in this case is boiling broth in the clay pot, a plate full of raw meat (and eggs, and sesame seeds). The basket of vegetables (which is sort of random and you can ask for specific greens from the display if you know which ones you prefer) and noodles, and then a few fiery condiments.
On to our second day. We walked over to Wat Ratchaburana in the morning. It has a enormous central tower (prang) and a pretty cool line of sight through the temple. (Small admission fee here as well)
The prang has intricate decorations including the obligatory naga and garuda birds such as this one. You can (and should) climb to the top of the prang. One reason is that you can see all of the architectural details much better.
Another reason is that you can descend a very steep staircase into the crypt where frescoes can still be seen on the walls. This will also satisfy your inner Indiana Jones for the day.
It's also worth wandering around the free part of the historical park. There are dozens of single tower wats standing here with trails and canals meandering through.