Many Khmer temples are actually scale models of the Hindu-Buddhist universe. Moats and walls symbolize oceans and mountain ranges that encircled the five-peaked Mount Meru, the lofty home of the gods. The majority of these temples face east to catch the rays of the rising sun, symbolic of life. The exception is Angkor Wat , which faces west, the direction of the setting sun and death. While the mathematical equations that dictated the dimensions of Khmer temples are no longer understood, it is known that the ancient Khmer placed great stock in the auspiciousness of such precise measurements. This can be discerned in the lay-out of Khmer temples, most of which possess a severe symmetry.

The building materials used by the ancient Khmer changed over time. Early Angkor-period temples were constructed of brick. Using a now-forgotten technique to cement the bricks together, the Khmer built towers that were similar in style to those built by the Cham in what is present-day central Vietnam. Examples of these early towers can be seen at Roluos, but the most impressive brick temple is Prasat Kravan , the interior of which has bas-reliefs carved right into the brick. A type of stucco made from such esoteric ingredients as pounded tamarind and the soft earth of termite mounds was used as a medium to sculpt ornamentation for the brick structures. Laterite, a porous stone that resembles lava rock, was utilized for foundations and walls. The use of sandstone was, of course, what set Khmer temples apart from religious architecture constructed by the ancient Cham, Thai and Burmese, all of whom worked almost exclusively in brick and stucco. As a medium for decoration, sandstone also allowed the wondrous talent of Khmer sculptors to shine through.

While the extent of sculpted motifs varies from temple to temple, two portions of Khmer edifices were always lavishly decorated: lintels and pediments. The lintel, a rectangular stone block fixed over doorways, became an important element in Khmer architecture when the Khmer began carving ornate designs into them several centuries before the Angkor period. Early prototypes have been found dating to the seventh century and indicate that the designs were influenced by pre-Angkor kingdoms such as Funan. As the styles and motifs have evolved over the centuries, experts on Khmer art are able to date lintels by comparing them to known works. A motif commonly found on lintels is Kala, an ogre-like temple guardian usually depicted with two stylized garlands spewing from the corners of his mouth. Often a deity or divinity is perched atop Kala's head. Pediments , the triangular space just above doorways and lintels, were also favourite spots for lavish adornment. Often these depict elaborate scenes from Hindu or Buddhist legends - the pediments at Angkor Wat and Banteay Srei being particularly fine examples. Framing the pediments are usually the undulating forms of nagas , long, multi-headed water serpents, issuing forth from the gaping mouths of makaras , another type of water beast. So popular was this particular architectural detail that it has survived to this day, and cobra-like nagas can be seen framing the pediments of modern temples in Cambodia as well as in neighbouring Thailand and Laos. Other images found in the vicinity of doorways are dvarapalas , standing male guardians usually depicted wielding a club or spear, and devatas , guardian female divinities. The realistically portrayed guardian images at Banteay Srei are thought by experts to be pinnacles of Khmer art. To many modern visitors, the most easily admired of the mythical representations are the apsaras , the celestial nymphs who seem to dance upon the smooth sandstone walls. Angkor Wat has by far the most sensitively rendered collection of apsaras and it is readily apparent that the artisans who sculpted these sublime images spent much time ensuring that no two were alike.

Apart from the images carved in bas-relief described above, "story telling" bas-reliefs were used to striking effect by the Khmer. Illustrating historical events, mythology (such as the Ramayana and Mahabharata) and exploits of the kings who had them commissioned, they cover over a thousand square metres of gallery walls in Angkor Wat alone. Depending on how they were executed, the bas-reliefs could be "read" like pages from a giant comic book, from panel to panel. Sometimes the bas-reliefs on a wall were divided into several levels, such as the depiction of the levels of heaven and hell found at Angkor Wat. Often though, a story or event was illustrated in a single large panel. As in Egyptian art, an image's importance is illustrated by its size in relation to the images around it. Thus the bas-reliefs at Angkor Wat depict grand images of the Hindu god Vishnu, his vehicle Garuda, and Vishnu's incarnations as Krishna, Rama and Kurma - evidence that Suryavarman II, the devaraja who had Angkor Wat commissioned, believed himself to be an incarnation of Vishnu on earth.

To Suryavarman II goes the credit for erecting ancient Cambodia's greatest architectural masterpiece, the silhouette of which graces the Cambodian national flag. Yet not long after his death, the Cham sacked Angkor and the empire fell into disarray. Not until a young prince, Jayavarman VII, took the throne and drove out the invaders was building to begin again in earnest. But major changes came with Jayavarman VII's reign that would affect Khmer architecture. The king's embrace of Buddhism caused the ascendancy of Mahayana Buddhism over Hinduism as the official religion. This is most readily seen in the mixed Buddhist and Hindu iconography of temples such as Ta Phrom and Preah Khan, where bas-reliefs depicting meditating Buddhas are found alongside the usual Hindu deities and demigods. At least, this would have been more apparent before Jayavarman VII's death. Following the Buddhist king's demise there was a backlash against Buddhism, and many of the carvings of meditating Buddhas at Ta Phrom and Preah Khan were defaced or recarved to resemble meditating Hindu ascetics.

Jayavarman VII's reign was also a time of vast territorial gains. Owing mainly to Jayavarman VII's rush to plant monuments across his newly expanded empire, the artisans and architects of the Bayon period have been accused by modern art historians of producing crude, hurried works. Laterite blocks were used in place of sandstone in the construction of many of Jayavarman VII's temples outside of the Angkor region. Because it was more easily quarried, laterite made it possible for Jayavarman VII to erect edifices in the more far-flung corners of his empire in a relatively short time. Unfortunately, the rough surface of laterite makes it impossible to carve reliefs upon. Stucco was used to decorate some of these laterite temples but the effect could never match the intricate bas-reliefs of carved sandstone. In the same vein, the bas-reliefs at the Bayon, Jayavarman VII's grandest monument, seem rather primitive when compared to the delicate intricacies of those at Angkor Wat. Despite the inferior quality of Jayavarman VII's works, there is one unique design innovation from his reign that many agree is the Khmers' most striking contribution to architecture: the colossal stone faces that gaze with blissful detachment from the towers of the Bayon and the gates of Angkor Thom. Thought to depict the Bodhisattva Lokeshvara, the Mahayana Buddhist 'Lord of Compassion', the faces can also be seen adorning gates at Banteay Kdei and Ta Phrom, as well as the towers of Banteay Chhmar in western Cambodia. Not surprisingly, this powerful visual theme - stone visages smiling enigmatically as the roots of mammoth banyan trees threaten to topple them into jumbled heaps - has been used extensively by modern artists, including several Hollywood film makers, to symbolise ancient civilizations lost to the ravages of time.

While the architecture of the ancient Khmer manages to inspire awe even in its ruined state, it is important to remember that when we look at the monuments today, we see only what did not perish with the centuries - stone, brick and stucco. What we don't see are the ornately carved pavilions of golden teak that housed troupes of court dancers, minstrels, high priests and the god-kings themselves. Gone are the decorative embellishments that would have brought the monuments to life: the sheets of gilded copper that covered unadorned stone walls and towers, the parasols, banners and tapestries of delicate silk that gave colour to dimly-lighted galleries and antechambers, the finely woven mats of aromatic grasses that covered rough stone causeways. Important elements which, when combined with the grandeur of bold stones rising up to dominate the jungle canopy, would surely have evoked paradise on earth