Driving along National Road 6 from Phnom Penh towards Kampong Thom and Siem Reap, one will spot the looming heads of stone serpents – or nagas – on the hundreds of ancient bridges built between the 10th and 14th centuries.

Acrhaeologists and researchers agree that while the names of the bridges may have changed since their establishment in the Angkor era, one can still tell apart the types of ancient bridges from their differing sizes.

“For example, a bridge that looks smaller is called a young bridge, or ‘Spean Khmeng’ and a bridge that is near water flow is called widow bridge or ‘Spean Memai’,”archeologist and deputy director of the Apsara Authority, Im Sok Rithy, said.

‘Spean’ gives the meaning of bridge in Khmer.

Among these bridges, Sok Rithy said, the longest bridge located along National Road 6, in the local Chi Kreng district, is the ‘Spean Preah Toeus’ bridge – or direction bridge – which was restored in the late 19th century by distinguished French researcher Bernard Philippe Groslier.

National Road 6, which recently underwent an upgrade and enlargement, was meticulously reconstructed with difficulty to avoid interfering with the ancient bridges’ structures. All along the 400-kilometre-long highway, hundreds of detours were specifically paved to avoid damaging the old bridges.

“A section of the new National 6 road, from Siem Reap to Kampong Thom, was forged on the remaining shape of the road built during the same time as the bridges – in the Angkor era,” he added.

An ongoing research study, the Living Angkor Road project, was started in 2005 to support anthropologists’ work on the Kingdom’s roads of relic. Endorsed by the Thailand Research Fund and the Authority for the Protection and Management of Angkor (Apsara Authority), the study involves anthropologists attributing the remaining portions of the age-old Angkor roads to the different provinces of the ancient Khmer empire.

Sok Rithy, who is closely associated with the project, said the bridges were constructed with stone, laterite – a reddish clay material – and sandstone.

“From what I know, the Ministry of Culture and Fine Arts (MCFA) is preserving and protecting these ancient bridges and what remains of their connecting infrastrucutre,” he said.

“Today, we are learning more about the role of local roads of that era and, more importantly, we want to know about the extent and scale of the Khmer empire.”

To preserve the relics of a once-grand and proud empire, MCFA spokesman Thai Norak Sathya said a lot of care had gone into the construction of the revamped National Road 6 to ensure that not a single inch of the old bridges were damaged in the process, citing the Spean Kampong Kdei bridge, which remains untouched.

“We haven’t placed ancient bridges on the cultural heritage list yet but the ministry works hard to preserve the ancient strucutres. Now, we only allow pedestriations and villagers who travel by motorbikes or bicycles to travel along the bridges,” Norak Sathya said.

Cars and other large vehicles are prohibited from wheeling onto the bridges – which, although have shown impressively enduring strength over the last hundreds of years, should not be vulnerable to excessive weight.