Pozzo di S. Patrizio, or the St. Patrick's Well, is a historic well in Orvieto, Umbria, central Italy, built between 1527 and 1537 at the behest of Pope Clement VII who had taken refuge at Orvieto during the sack of Rome by the Holy Roman Emperor Charles V. Fearing that the city’s water supply would be insufficient in the event of a siege, the Pope assigned the task to architect-engineer Antonio da Sangallo, who had worked extensively in Rome during the Renaissance.

Hailed as a masterpiece of hydraulic engineering, the cylindrical well plunges down more than 50 meters in a double helix design, carrying two one-way staircases one going up and another going down. This allows people and donkeys loaded with water vessels to move without obstruction. At the bottom is a bridge where people could walk on and scoop out water. Large windows, placed diametrically opposite to each other, light the staircases naturally. This design was unique at the time, because there are no other wells like it anywhere in Europe.

Photo credit: orso/Panoramio