Archaeologists excavating the ancient Hittite capital city of Alacahöyük, in western Turkey, have unearthed a 2300-year-old secret tunnel. The team was excavating a sanctuary that had been previously discovered in 2014, when they uncovered the tunnel, also known as a potern. So far, 23 meters of the tunnel have been dug and cleaned, but excavators believe it is longer still. These secret tunnels were often dug beneath the castle, and extended into the city. Because this potern is located under a sanctuary, the archaeological team believes it may have had a sacred purpose.