Archaeologists are scratching their heads about an underground pyramid-shaped structure they have been excavating beneath the historic medieval town of Orvieto in Italy. But it may not be a mystery forever. They hope to find answers as they continue to tease artifacts and architectural materials from the soil.

"We discovered it three summers ago and still have no idea what it is," write Prof. David B. George of St. Anselm College and co-director Claudio Bizzarri of PAAO and colleagues about the site. "We do know what it is not. It is not a quarry; it's walls are too well dressed. It is not a well or cistern; its walls have no evidence of hydraulic treatments."

Read more

Source: http://popular-archaeology.com/