Built during the reign of King Narai the Great, this royal residence is situated on an island in Thale Chup Son, serving as a summer retreat. Its architecture uniquely blends Thai-style lotus-petal arched windows within a European masonry structure. It held paramount significance as an observatory, where King Narai hosted French ambassadors and astronomers. This was the site for observing the lunar eclipse (1685) and the solar eclipse (1688), marking the dawn of modern astronomy in Thailand. Although only ruins remain today, the site retains its grandeur and stands as a key historical landmark reflecting Lavo's golden age.