Directly across the road from Wat Ratburana lies the temple of Wat Mahathat. The temple was built in the early days of Ayutthaya in the late 14th century by King Borommaracha I. The story goes that the king had a revelation, and relics of the Buddha then suddenly appeared. The temple was built to house the relics.
Little remains today except the core of the old prang and a few smaller chedis. It is nonetheless impressive.