Wat Ounalom, made up of 44 different structures, was built in 1443 to house the hair of an eyebrow of Buddha. The sanctuary has also long served as the residence of the patriarch of the monastic community. It used to house the library of the Buddhist Institute and its huge book collection, which is probably why it was laid to waste by the Khmer Rouge. You'll notice a few contemporary bas-reliefs inspired by Angkor Wat in the cemetery behind the vihear.