Wat Mahathat is the most important and impressive temple compound in Sukhothai Historical Park. ‘Wat Mahathat’ translates as ‘temple of the great relic’ and many Thai cities have a Wat Mahathat, where relics of the Buddha were kept.
When evaluating the Sukhothai Inscriptions (on stone) Wat Mahathat was built somewhere in between 1292 and 1347.
Wat Mahathat is the first temple complex you see when entering the historical park from the east. There are many temple structures, a lot of them have been restored during the 20th century. So some of the decorations may not exactly be as old as you might have imagined. You would need a thorough guidebook or someone with archaeologic knowledge to figure out exactly what is as it used to be, and what has been restored.