Sitting roughly halfway between the cities of Bangkok and Chiang Mai, Sukhothai is one of the first capitals of the ancient Thai empire. The ancient city is now in ruins, but the remains now make up the UNESCO World Heritage Sukhothai Historical Park.
The entire park covers a total area of 70 kilometers and contains 193 total ruins. Most of the important sites are located within the 2km square old city walls. And, the most important site within the city walls is Wat Mahathat.
Originally built in the 13th century, the grounds of the large site feature several large Buddha statues and many grand chedis. The above photo of Wat Mahathat shows one of the main Buddha statues in the Sukhothai Historical Park as well as the surrounding ruins.
I would highly recommend a stop in Sukhothai for anyone interested in history or ruins that is visiting Thailand.