Wat Arun, locally known as Wat Chaeng,
is situated on the west (Thonburi) bank of the Chao Phraya River.
It is believed that after fighting his way out of Ayutthaya,
which was besieged by a Burmese army at the time,
King Taksin arrived at this temple just as dawn was breaking.
He later had the temple renovated and renamed it Wat Chaeng, the Temple of the Dawn.
During his reign (Thonburi Period),
Wat Chaeng was the chief temple,
and it once enshrined the Emerald Buddha
and another important Buddha image, the Phra Bang,
both of which had been removed from Vientiane.
It has an imposing spire over 70 metres high,
beautifully decorated with tiny pieces of coloured glass
and Chinese porcelain placed delicately into intricate patterns.
Although it is known as the Temple of the Dawn,
t's absolutely stunning at sunset, particularly when lit up at night.
Source:
http://www.bangkok.com/attraction-temple/wat-arun.htm