Khlong Phadung Krung Kasem

It was dug in 1851 in order to serve as a new outer moat for the expanding city, extending its boundaries from the Rattanakosin Island to the north and east.

By the time of King Mongkut (Rama IV)'s reign, the city had outgrown its original area, and in 1851 the King ordered the digging of another canal, roughly parallel to the old moat, from Wat Thewarat Kunchon to Wat Kaeo Fa.

The construction, headed by Chaophraya Si Suriyawong, was completed the following year, and the King named the canal Khlong Phadung Krung Kasem, roughly meaning "the canal upholding the city's happiness".

As the political climate and military practices had vastly changed by then, defensive walls were no longer deemed necessary, although seven forts were nevertheless built along the canal (plus one on the western bank opposite the canal's mouth).

The expansion more than doubled the city area, to 5,552 rai (8.883 km2; 3.430 sq mi).