Wat Phra Mahathat Vihan is the most important temple of Nakhon Si Thammarat and southern Thailand. It was constructed at the time of the founding of the town, and contains a tooth relic of Buddha. The 78 m high chedi is surrounded by 173 smaller ones. While the chedi is now in Sri Lankan style, it is said to be built on top of an earlier Srivijaya style chedi. The chedi completed a renovation in early 2009 and now appears like new.
At the base of the chedi is a gallery named Viharn Tap Kaset, decorated with many Buddha statues and elephant heads emerging from the chedi. Viharn Phra Song Ma is the buildings which contains the staircase which leads to a walkway around the chedi above the gallery. At the bottom of the staircase are demon giants (yak) as guardians. Adjoining to the north is the Viharn Kien, which contains a small temple museum.
South of the chedi is the large ubosot building, the Viharn Luang. Monk living quarters are located across the street in a separate temple, Wat Na Phra Boromathat.
The chedi is the symbol of the Nakhon Si Thammarat province, present in the seal of the province. It is also displayed on the 25 satang coin.