Record flooding has turned Ayutthaya's ancient temples into islands, and a giant statue of the reclining Buddha appears to float miraculously on the lapping water. Experts fear that at least half of the more than 200 waterlogged monasteries, fortresses and other monuments in the one-time royal capital have been damaged.
"Imagine a thousand tons of brick and stone resting on soft foundations, with no modern-style pilings. We are very worried," said Chaiyanand Busayarat, director of the Ayutthaya Historic Park.
And as flood waters recede, some experts are proposing a radical change to prevent similar disasters in the future: Turn back the clock about four centuries to emulate the city's urban planners and engineers of that time.
"We can't prevent flooding so we have to learn to live with water again, like those who created Ayutthaya. Let's take out the old city maps," said Anek Sihamat, deputy director-general of the Thai government's Fine Arts Department.
He recommended digging up old canals that have been paved over for roads and curbing the urban sprawl and industrial parks that block the natural runoff of water.
Capital of a powerful state for 417 years, seat of 33 kings, Ayutthaya has been described as one of the greatest cities on water ever, with a canal network that measured more than 85 miles (140 kilometres). Built on the flood plain of central Thailand at the confluence of three rivers, it was inundated annually, but its citizens lived in stilt-raised houses and used boats for transport.
Water also defended Ayutthaya, which once held as many as 1 million residents, until a brutal sacking by the Burmese in 1767 forced relocation of the capital to Bangkok, 50 miles (80 kilometres) to the south — where the same floodwaters that inundated Ayutthaya are now nearing the inner city.
The surge of water from the northern highlands, which began in late July and has killed more than 520 people, is the worst since the 1940s, although Ayutthaya experiences flooding almost every monsoon season.
In coming weeks, experts will assess damage and determine what will be needed to revive and protect the city, which was added to the UNESCO World Heritage list in 1991.
Advisers from Venice and the Netherlands, two places that have grappled with the challenges of watery environments, are prepared to come, while several countries, including Germany and Japan, have provided or promised funds. Anek, the Fine Arts official, estimated that some $20 million will be needed.
"Clearly what we hope for from this experience will be a more solid, more thorough flood mitigation plan," said Tim Curtis, head of the culture unit at UNESCO's regional office in Bangkok.
He said that Amsterdam's 19th-century water-based defense line — another World Heritage site — and Venice may be used as models.
Witthaya Pewpong, the Ayutthaya provincial governor, said a dam has been proposed to shield the historic area while flooding would be eased by setting aside a large, construction-free area of the nearby countryside to absorb excess water.
Nevertheless, authorities "know that they will have to learn to live with water because it will always be there," said UNESCO cultural expert Montira Horayangura Unakul. As such, urban planning should be consistent with Ayutthaya's design as a city of water, she said.
To date, Ayutthaya has not scored well on the urban management front. The city of 82,000 people is mushrooming helter-skelter and has bid to host World Expo 2020. Four years ago, amid concern in Thailand that UNESCO might take the city off its list, one Bangkok newspaper wrote that the city was destroyed twice, "first by invading Burmese, and now by greedy and insensitive Thais."
Adding to its watery woes, said Curtis, are problems common to heritage sites: the looting of artifacts, inadequate waste disposal, corrosive vehicle fumes, ugly and inappropriate new construction and mass tourism.
There's also a running battle between heritage and municipal authorities, often allied with business interests.
The Fine Arts Department controls development in the core historic area of some 1.2 square miles (3 square kilometers), where no structures more than 26 feet (8 meters) are permitted. However, it exercises little power in outlying zones, which include numerous important monuments and where modern buildings have sprouted next to graceful relics of the past.
Most immediately, however, heritage authorities are focused on the floods.
With water up to 10 feet (3 meters) high flooding the area for weeks, there is concern that the foundations of larger structures may have been undermined, and bricks, plasterwork and murals damaged. Visitor facilities and once grassy areas emerging as a sea of mud will need to be restored at what is one of the country's top tourist destinations.
Also worrisome is salt residue that seeps up with the groundwater, causing damage to monuments.
Park director Chaiyanand said the stupas, or Buddhist reliquary, in Ayutthaya were built with an outer core of brick. The hollow portions inside were filled with sand. When the floods came, the water was absorbed upward into this inner chamber of sand, which became heavier. He fears the weight could cause cracks of the outer brick shell.
Water that is hard to detect and remove may also remain within walls after the floodwaters recede. Chaiyanand said he was particularly concerned about the bricks that were the key building blocks of old Ayutthaya.
"They're like crackers," he said, noting the mossy, water-stained bricks at the base of a stupa at the 15th-century Phra Srisanphet monastery. "When soaked they become easy to break."