[snogglethorpe]

From the wikipedia page on Hōryū-ji (http://en.wikipedia.org/wiki/H%C5%8Dry%C5%AB-ji):

``... The original temple, named by modern historians and archaeologists Wakakusa-garan (若草伽藍), was lost, probably burned to the ground after being hit by lightning in 670. The temple was reconstructed but slightly reoriented in a northwest position, which is believed to have been completed by around 711. The temple was repaired and reassembled in the early twelfth century, in 1374, and 1603. ... The five-story pagoda, located in Sai-in area, stands at 32.45 meters in height (122 feet) and is approximately 20X20 in width and is one of the oldest wooden buildings in the world. The wood used in the center pillar of the pagoda is estimated through a dendrochronological analysis to have been felled in 594.''

No doubt some other buildings may be older.

In summary: really frickin old... :]