Ratchadamnoen means the royal passage, because it links between the Grand Palace and Dusit Palace.
There are three parts :
Ratchadamnoen Nai or inner avenue, started from The Grand Palace lies along Sanam Luang to Ratchadamnoen Klang.
Ratchadamnoen Klang, the middle part or central avenue, was the widest road at that time, was built during King Rama V reign (1868-1910) links Ratchadamnoen Nai and Ratchadamnoen Nok. Started from Sanamluang to The Golden Mount. Democracy Monument is the remarkable point on Ratchadamnoen Klang.
Ratchadamnoen Nok or outer avenue, near Dusit Palace, started from The Golden Mount straighten to the Ananta Samakhom Throne Hall. Today Ratchadamnoen Avenue is the centre government administration. Most Government departments are located around this area, U.N. and ESCAP organizations are also situsted on Ratchadamnoen Nok Road