"Khlong Ong Ang is a part of Khlong Rob Krung starting from Khlong Bang Lamphu at Phan Fa Lilat Bridge and ending at Chao Phraya River near Bophitphimuk Worawihan Temple. This canal makes a boundary line between Phra Nakhon District and Samphanthawong District. The canal was dug in the reign of King Phra Budda Yodfa Chulalok (King Rama 1) when His Majesty ordered to build the Grand Palace and expanded the capital to wider area. Later in 1783, coinciding with the Year of the Rabbit, His Majesty gave order to dig Khlong Khu Muang Derm by connecting the Northern Chao Phraya River at Bang Lamphu Subdistrict passed Bowonniwet Rathaworawihan Temple, Thepthidaram Worawihan Temple, Saket Temple and Burapha Phirom Palace to the southern Chao Phraya River above Sam Pluem Temple or Chakrawat Rachawat Woramahawihan Temple. Total length is about 3.426 kilometers, width about 20 meters and dept about 2.5 meters. Walls, city gates and forts were also built along the inner canal riverside. Along the canal riverside, there were city gates and forts that spaced intervals to 9 ranges for an outer moat canal. After digging the canal, the city area becomes an island surrounded by water, on the west side is Chao Phraya River and on the east side is Khlong Rob Krung."
