Hi-tech technique reveals hidden 'graffiti' on walls of Angkor Wat

Every year millions of tourists flock to Angkor, the magnificent temple complex which forms the spiritual heart of Cambodia.

Visitors marvel at the dizzying scale of the ruins and admire the intricately carved bas-relief friezes that adorn the walls - but there are numerous artistic creations that they fail to see.

Cutting-edge digital photographic techniques have recently revealed masses of paintings on the walls of the 900-year-old temple that are invisible to the naked eye. Despite extensive study by archaeologists over the years, many of them have never been noticed before.

Four years ago Noel Hidalgo Tan, a PhD candidate at the Australian National University and specialist in the rock art of Southeast Asia, made the startling discovery.

"In 2010 I'd just finished my master's degree and was spending three weeks working as a volunteer on excavations at Angkor Wat," Tan told the South China Morning Post.

"One day I was wandering around the temple during my lunch break when I noticed some smudges on a rock. I took photos of them because I thought there might be something there. When I looked at the images on my computer later, I was surprised to see some really quite elaborate paintings."