Prang Khaek is considered the oldest historical site in Lopburi, built during the 10th century (15th Buddhist Century) in the Khmer Pakhua style. Its standout feature is the three brick towers constructed using an ancient mortarless technique, where bricks were rubbed smooth and stacked tightly. This site was originally established as a Hindu shrine long before Lopburi became a major center for the Khmer and Ayutthaya empires. Although it underwent major restoration during the reign of King Narai the Great, the original structure clearly reflects its 1,000-year-old heritage. This monument serves as vital evidence confirming the long-standing prosperity of ancient communities living in the Chao Phraya River basin.