This oldest and largest Pho tree of the country is located in Wat Ton Pho Si Maha Pho. It has been recorded that , 2000 years ago, the seedling stock of this Pho tree was brought over from Buddhakaya. The tree is about 20 metres in circumference, about 30 metres in height, and about 25 metres in diametre.

From the legend, Phra Chao Tawa Nam Payadit, the ruler of Mueang Mahosot had sent his representatives to Nakhon Patulibut of India for a branch of the Pho tree, under which the Lord Buddha had sat during his enlightenment. Thereafter, the branch had been planted at this Wat Ton Pho Si Maha Phot. This Pho tree has been the symbol of Prachin Buri. On Visak Puja Day, there will be a fair to commemorate this Pho tree. From Prachin Buri town, use Highway No.319 to Phanom Sarakam for 32 kilometres, turn left for 1 kilometre.