Wat Phra Kaew (วัดพระแก้ว), the Temple of the Emerald Buddha, and the adjoining Grand Palace together form the greatest spectacle for the visitor to Bangkok. Despite the fact that the whole compound is so full of tourists you spend half the time trying to avoid getting in people's photos, it's still a pretty amazing place to visit. It consists of over 100 brightly colored buildings, golden spires and glittering mosaics, and dates back to 1782, when Bangkok was founded. When you enter the compound, you first of all see Wat Phra Kaew and the nearby attractions, and then move on to the Grand Palace afterwards.
Wat Phra Kaew itself is the main attraction though. This is Thailand's most important and sacred temple, so you're expected to act with due respect inside it. It houses the tiny (between 60 and 75 cm) Emerald Buddha, which is located high above the heads of the worshippers and tourists. Not much is known for certain about the statue, except that it isn't actually made of emerald but rather of green jade or jasper. Getting a good look at it is difficult as photography is forbidden inside the temple, and it's perched so high up inside it's glass box that it's difficult to really see.
It's thought to have been made in the 15th century and was the cause of several wars before ending up for good in Bangkok in 1782. The image is considered a talisman and holds tremendous significance for Thailand and the Thais. The 'robe' that it wears is changed 3 times each year by the King himself, at the start of each season: A diamond encrusted gold robe during the hot season, a solid gold robe in the cool season and a gilded monk's robe in the rainy season.There are also many other Buddha images inside the temple.