The Wat Phra Kaew = Temple of the Emerald Buddha; full official name Wat Phra Si Rattana Satsadaram, is regarded as the most sacred Buddhist temple in Thailand. It is a "potent religio-political symbol and the palladium [safeguard] ofThai society. It is located in the historic centre of Bangkok (district Phra Nakhon), within the precincts of the Grand Palace.

The main building is the central ubosoth, which houses the statue of Emerald Buddha. The legendary history of this Buddha image is traced to India, five centuries after the Lord Buddha attained Nirvana, till it was finally enshrined in Bangkok at the Wat Phra Kaew temple in 1782 during Rama I's reign (1782–1809). This marked the beginning and raise of the Chakri Dynasty of the present Kingdom of Thailand(the present head of the dynasty is King Rama IX. The Emerald Buddha, a dark green statue, is in a standing form, about 66 centimetres (26 in) tall, carved from a single jade stone (Emerald in Thai means deep green colour and not the specific stone). It is carved in the meditating posture in the style of the Lanna school of the northern Thailand. Except for the Thai King, no other person is allowed to touch the statue. The King changes the cloak around the statue three times a year, corresponding to the summer, winter, and rainy seasons, an important ritual performed to usher good fortune to the country during each season. (ref

Fee: 500 Baht (as of May 2013, a little bit pricey but that there's a lot to see inside)

Note: The rules of entry and conduct are very strict hence a dress code is followed.  Short shorts and skirts and sleeveless are not allowed inside, though there are some shops outside that sells loose cotton trousers (for souvenir) or you can rent them, which would cost you about 20 Baht for the rent and 100 Baht refundable deposit. You will be asked to take off your shoes before entering the temples, it is to show respect to the Buddha. When you sit, you must be careful not to point your feet to the deity, it must tucked in towards the back. This is very common to any sacred temples in Thailand.

Maps are available when you purchase the tickets. 

One of the demon guards at the entrance to the main grounds.

A part of the paintings on the wall. 
The Phra Sri Ratana Chedi,, a 19th-century stupa built in Sri Lankan style where the ashes of the Buddha is kept.

Phra Mondop, a library in Thai style built by Rama I

External decorations of the main building. An army of Garudas and Nagas.

One of the two Golden Phra Chedis, constructed by King Rama I in honor of his father  and mother.

Demon guardian of the Golden Chedi.

Palace guards.

Chakri Maha Prasat Hall

Wat Phra Kaew sunset.
I've no pictures of the Emerald Buddha, Queen Sirikit Textile Museum and The Royal Thai Decorations and Coins Pavilion as taking pictures were not allowed in this area.