Sadly a great deal of the Lao built heritage has long since disappeared. Constructed mainly of wood prior to the 19th century, many palaces and temples ultimately fell victim to the tropical climate, but the great majority were destroyed by plundering neighbours. Much of what now remains is of fairly recent origin, rebuilt completely using modern techniques and materials rather than reconstructed in accordance with traditional methods and styles. Despite this fact, there remain numerous important heritage sites, which range from clusters of ancient standing stones and burial urns to graceful Khmer temple complexes, elegant Buddhist wats (temples), stilted domestic dwellings and French colonial residences.
The earliest surviving man-made structures in Laos are the groups of standing stones and associated burial chambers at Hintang Houamuang in Houaphanh Province and Hintang Nalae in Luang Namtha Province (1000-500 BCE) and the clusters of stone jars at the Plain of Jars in Xieng Khouang Province (4th-2nd centuries BCE), all of which are believed to have functioned as prehistoric aristocratic necropolises.
The formation of petty kingdoms during the late prehistoric period necessitated the construction of large defensive fortresses, and as time went on their construction became more and more intricate, featuring substantial moated earthworks with wooden pallisades. With the development of larger kingdoms during the first millennium CE, elaborate royal palaces also began to make an appearance, but since these were constructed mainly from wood and other perishable materials, those not destroyed in countless wars would eventually have succumbed to the tropical climate. Early Hindu and Buddhist temples were initially established mainly in forest areas, often on the site of ancient animist shrines; many were located in caves or beneath rocky overhangs, while others were protected by thatched wooden canopies. Thereafter under royal patronage masonry steadily replaced wood and thatch as the principal construction material for religious buildings.
By the 3rd century CE the Mon had established a major city-state at Nakhon Pathom, west of Bangkok, from which they gradually built up a large mandala known as Dvaravati (6th-11th centuries), which stretched from southern Burma across what is now central Thailand. In 769 Dvaravati extended its power northwards to the present-day northern Thai city of Lamphun near Chiang Mai, where it founded the kingdom of Haripunjaya. The proliferation of ancient Buddhist sites marked by Dvaravati-style bai sema (temple boundary stones) found along the middle reaches of the Mekong River in what is now central Laos suggests that during this very same period the Mon also extended their sphere of influence eastwards from Haripunjaya through the modern Lao provinces of Bokeo, Sayaburi, Vientiane, Saysomboun, Borikhamxai and Khammouane. Mon city states established in this region included Souvannakhomkham in modern Bokeo Province, Candapuri (Chanthaburi, later the capital city of Vientiane) and neighbouring Sayfong in present-day Vientiane Prefecture, Phainam (later Viengkham) in modern Vientiane Province and Sri Gotapura (later Sikhottabong) in present-day Khammouane Province. Muang Sua (the original name for Luang Prabang) is also believed to have originated as a Mon settlement. The Mon played a crucial role in the propagation of Therevada Buddhism throughout the wider region, laying the groundwork for its subsequent consolidation as the state religion under the Fa Ngum dynasty of Lane Xang.
During the same period the provinces which now make up southern Laos fell under the control of the emerging Khmer empire. Recent archaeological work in the vicinity of the Khmer temple complex of Wat Phu Champassak in modern Champassak Province suggests that between the 5th and the 7th centuries CE the nearby ancient city of Setapura functioned either as the capital or at least as a major centre of the proto-Khmer kingdom of Upper (Land) Chenla. Upper Chenla later merged with its Mekong Delta-based sister kingdom of Lower (Water) Chenla, giving rise to a unified Khmer state ruled initially from Phnom Kulen and subsequently from Angkor. Between the 9th and the 13th centuries the powerful Angkorian kings expanded their sphere of influence across much of the region, constructing a vast network of temple complexes, the architecture of which was designed to support their claims to divine kingship.
Featuring elaborately carved causeways, courtyards and galleries decorated with magnificent bas-reliefs (engravings raised from their background), the magnificent architecture of Wat Phu Champassak itself was intended to inspire worshippers both before and after ritual ceremonies. From the earlier Hindu temples to the later Mahayana Buddhist edifices, the architecture of the Khmer temple had a singular purpose – to recreate an entire cosmology here on earth, represented by a succession of concentric mountain ranges and seas surrounding a central continent, out of which rose Mount Meru, the five-peaked home of the gods.