Bangkok is younger than it looks. The Thai capital only moved to this bend of the Chao Phraya in 1782, when King Rama I (the first king of the Chakri dynasty, which still reigns) left the west bank and started building a palace on the east bank, partly with bricks salvaged from the ruins of Ayutthaya. Today about 11 million people live in a city that stacks gold-leaf temples, glass malls, wooden canal houses and six-lane expressways on top of each other, often on the same block.
It's loud, hot, and bigger than any first-timer expects, and it rewards a plan. The temples are best at 8 in the morning, before the heat and the tour buses. Midday is for air-conditioning, a massage or a boat. Evenings are for food, because Bangkok eats late and everywhere. Five days lets you do the royal sights without a forced march, fit in a weekend market, a floating market and a Muay Thai night, and still spend a day at the ruins of Ayutthaya, the old capital that Bangkok replaced.
Day one is royal Bangkok and the river, day two Chatuchak, Jim Thompson House and the skyscrapers, day three a floating market, the old city and a fight night, day four Ayutthaya, and day five Chinatown. Start on a Friday: Chatuchak and Khlong Lat Mayom mostly run at weekends, so Saturday and Sunday are spoken for. Bangkok is also the front door to Thailand, and most of what you'll eat here is the national cuisine at its best.