The Ħal-Saflieni Hypogeum is a remarkable subterranean structure dating back to the Saflieni phase (3300 – 3000 BC) of Maltese prehistory. Discovered accidentally in 1902, this UNESCO World Heritage Site is thought to have served as both a sanctuary and a necropolis, with over 7,000 individuals documented by archaeologists. It stands as one of the best-preserved monuments of the temple-building culture of Malta, which also includes the famous Megalithic Temples and the Xagħra Stone Circle.