Bangkok was originally moated and walled with forts at intervals along it. The
moat was formed by a canal dug at a distance of about two kilometres from the Royal Palace
, leaving the river to the north of the city and rejoining it to the south. It is 7.2
kilometres long, and it is today called Klong Bang Lamphu and Khlong Ong Ang. Strong
and solid walls were constructed along the inner side of this canal, being 3.6 metres high
and 2.7 metres thich, broken by 16 gates and 14 forts (Phra Sumain, Yukornton, Mahaprab, Mahakan, Mootaluog, Seurtayan,
Mahachai, charkphet, Phisua, Mahaluok, Mahayak, Phrachun, Phra-Ar-thit, and Isintorn), two of which now remain as histiric
monuments on the 200 metres, remaining of the wall, namely, Fort Mahakan and Fort Phrasumain.