The network of cities might be as big as Cambodia's capital city

Archaeologists have turned up the remains of a network of medieval cities lost in Cambodia's jungle, a network so large that it could rival the size of capital city Phnom Penh.

The discovery was made near the popular tourist destination of Angkor Wat, a UNESCO world heritage site. Despite the temple complex's popularity with visitors, much of the area is covered by thick rainforest, making any archaeological work there incredibly difficult.

Angkor Wat temple complex, Cambodia

A team of scientists employed light detection and ranging (LIDAR) technology, which essentially means shooting lasers at the ground from a helicopter. Dense forest canopies are no obstacle to the tech, and so the archeologists were able to see the remains of city centres, water channels, and an extensive system of roads.

"We have entire cities discovered beneath the forest that no one knew were there," said study author Dr. Damian Evans to The Guardian. "This time we got the whole deal and it's big, the size of Phnom Penh big."

The big discovery has big historical implications. The inter-connected cities may represent the largest empire on the planet in the 12th century, beating out the Roman Empire and China's Song dynasty. The discovery could provide clues as to why the Khmer civilisation collapsed in the 15th century. 

Cambodia has only been open to visitors for a short time, which means there may still be a lot more in the jungle waiting to be discovered.