Each year, millions of visitors flock to Angkor Wat, an ancient temple in modern-day Cambodia. There, they marvel at the 900-year-old towers, a giant moat and the shallow relief sculptures of Hindu gods. But what they can't see are 200 hidden paintings on the temple walls.
New, digitally enhanced images reveal detailed murals at Angkor Wat showing elephants, deities, boats, orchestral ensembles and people riding horses — all invisible to the naked eye.
Many of the faded markings could be graffiti left behind by pilgrims after Angkor Wat was abandoned in the 15th century. But the more elaborate paintings may be relics of the earliest attempts to restore the temple, researchers said. [See Photos of Angkor Wat's Secret Paintings]
Subtle traces of paint caught the eye of Noel Hidalgo Tan, a rock-art researcher at Australian National University in Canberra, while he was working on an excavation at Angkor Wat in 2010.
Built between A.D. 1113 and 1150, Angkor Wat stood at the center of Angkor, the capital of the Khmer Empire. The 500-acre (200 hectares) complex, one of the largest religious monuments ever erected, originally served as a Hindu templededicated to the god Vishnu, but was transformed into a Buddhist temple in the 14th century.
Tan said he kept spotting traces of red pigment all over the walls when he was taking a stroll through the temple on his lunch break one day. He took a few pictures and planned to digitally enhance them later.
"I didn't realize that the images would be so detailed, so I was naturally taken aback," Tan told Live Science in an email.
The digitally enhanced pictures revealed paintings of elephants, lions, the Hindu monkey god Hanuman, boats and buildings — perhaps even images of Angkor Wat itself. Tan went back to the site to conduct a more methodical survey in 2012 with his Cambodian colleagues from APSARA (which stands for the Authority for the Protection and Management of Angkor and the Region of Siem Reap).
"Some of the most detailed paintings, the ones located at the top of the temple, are passed by literally thousands of visitors every day, but the most elaborate scenes are effectively invisible to the naked eye," Tan said in an email.
To make these paintings visible, Tan used a technique called decorrelation stretch analysis, which exaggerates subtle color differences. This method has become a valuable tool in rock-art research, as it can help distinguish faint images from the underlying rock. It has even been used to enhance images taken of the Martian surface by NASA's Opportunity rover.
One chamber in the highest tier of Angkor Wat's central tower, known as the Bakan, contains an elaborate scene of a traditional Khmer musical ensemble known as the pinpeat, which is made up of different gongs, xylophones, wind instruments and other percussion instruments. In the same chamber, there's an intricate scene featuring people riding horses between two structures, which might be temples. [Image Gallery: How Technology Reveals Hidden Art Treasures]
"A lot of the visible paintings on the walls have been previously discounted as graffiti, and I certainly agree with this interpretation, but there are another set of paintings discovered from this study that are so schematic and elaborate that they are likely not random graffiti, but an attempt to decorate the walls of the temple," Tan said.
The findings were detailed in the journal Antiquity this week.