Bangkok is the capital of Thailand and by far its largest city with an estimated population of over 10 million.
Bangkok (originally Bang Makok) was a small village on the banks of the Chao Phraya river, until a new capital was founded on the west bank (present-day Thonburi) after the fall of Ayutthaya. In 1782, King Rama I built a palace on the east bank (now Rattanakosin) and renamed the city as Krung Thep, as it is now known to Thais -- the City of Angels (and much more: the full name is listed as the world's longest place name by the Guinness Book of Records
Bangkok is a large city, rising vertically and growing horizontally. Administratively it is split up into 50 khet (districts), but these are more often used in official business and for addresses. Visitors will find the conceptual division below more useful.
Sukhumvit – The long Sukhumvit Road, changing name to Ploenchit Road and Rama I Road going west, is Bangkok's modern commercial core, full of glitzy malls and hotels. The Skytrain intersection at Siam Square is the closest thing Bangkok has to a centre.
Silom – To the south of Sukhumvit, the area around Silom Road and Sathorn Road is Thailand's sober financial center by day, but Bangkok's primary party district by night when quarters like the infamous Patpong come alive.
Rattanakosin – Between the river and Sukhumvit lies the densely packed "Old Bangkok", home to Bangkok's best-known wats. Yaowarat (Chinatown) and sights around the Chao Phraya River are also included here. Bangkok's backpacker mecca Khao San Road and the surrounding district of Banglamphu are located on the northern part of Rattanakosin.
Thonburi – The quieter west bank of the Chao Phraya River, with many small canals and some offbeat attractions.
Phahonyothin – The area around Phahonyothin Road and Viphavadi Rangsit Road is best known for the Chatuchak Weekend Market and Don Muang Airport.
Ratchadaphisek – The district north of Sukhumvit centered around Ratchadaphisek Road (part of which is called Asoke) and reaching from Phetchaburi Road to Lat Phrao. This area has really opened up recently as the new metro line follows Ratchadaphisek Road.