Wat Yai Chai-mongkol      Wat Phra chao Phya-thai, populary known as Wat Yai Chai-mongkol, is situated to the southeast of the city, The large chedi there can be seen from a great distance. This monastery was built by King U-thong in 1357 A.D. for the use of the monks who had returned from Ceylon after studying under Phra Vanarat Maha Thera. This body of Monks was known as the Pa kaeo Sect. So this monastery was originally known as Wat Pa Kaeo. The monks of this sect were engaged mainly in meditation, Many people who respected these monks joined their order. The king conferred the title of Somdej Phra Vanarat on the head of the sect, and appointed him The patriarch on the Right Hand side. He was on a par with Somdej Phra Buddha-kosacharn. Who headed the sect mainly engaged in study of the scripture. And was known as the Patriarch on the Left Hand Side. This monastery was the place where the patriarch stayed. So it was also named Wat chao Phya-thai which means The Temple of the supreme Patriarch.      At one time, in the bot (convocation hall) of this monastery, Prince Thian-raja (later King Maha Chakraphat) sought to learn his luck through the ordeal of the lighted candles before he dethroned Khum vora-wongsa. On another occasion Prince Srl-silp consulted Somdej Phra Vanarat of this Monastery about a favourable moment for overthrowing King Maha Chakraphat in 1561 A.D.      In 1592 A.D.,during the reign of King Naresuen the Great, the Burmeseled an army to try to subjugate Ayutthaya. King Naresuen the Great resisted the invasion and fought in single-handed combat on elephant back with the burmese leader at the district of Nong Sarai in the province of suphanburi, and gained the victory by cutting down his opponent. On that occasion. King Naresuen the Greats army was not able to inflict severe losses on the enemy because many of his regiments did not come to reinforce his im time. King Naresuen the Great wished to execute the officers of those regiments at the conclusion of the war, but Patriarch Vanarat begged the King to pardon them and advised him to build chedis in memory of his great victory. So the King built one on the scene of the single-handed combat at Nong Sarai in the province of Suphanburi. And a built by King Naresuen the Great was named Phra Chedi Chai-mongkol, or chedia of the Auspicious Victory, buy it was popularly known as APhra Chedi Yai, or the Great Pagoda. So.later on Chao Phya-Thai came to be known also as Wat Yai Chai-mongkol. The top of this chedi is visible to tourists from Bangkol as soon as they enter the boundary of Ayutthaya