When construction workers in Malta broke through a layer of limestone in 1902, they expected to find little more than space for a new housing development.
Instead, they stumbled upon one of the most extraordinary archaeological discoveries in Europe.
Hidden beneath the town of Paola was a vast underground complex unlike anything previously known on the islands.
Today, the Hal Saflieni Hypogeum is recognised as the world's only known prehistoric subterranean temple and a UNESCO World Heritage Site.
Carved thousands of years before the Roman Empire and predating many famous ancient monuments, the site has fuelled generations of speculation.
