Pozzo di San Patrizio (St Patrick's Well), Orvieto

The Pozzo di San Patrizio is one of the marvels of Renaissance engineering, a cylindrical well sunk 62 metres into the tufa beside Piazza Cahen in Orvieto. It was commissioned by Pope Clement VII, who took refuge in the town after the 1527 Sack of Rome and wanted to guarantee the water supply should Orvieto ever be besieged; the architect Antonio da Sangallo the Younger designed it, and it was completed in 1537. The genius of the design lies inside: two separate spiral staircases wind around the shaft in a double helix, so that mules carrying empty containers could descend by one stair and climb back up the other without ever meeting, lit by seventy-two large windows that open onto the central void. Visitors today walk down all 248 steps of one helix to a small bridge across the water at the very bottom, then climb the second stair back to the surface, looking across the well to the people moving on the opposite ramp. The descent and ascent together take around forty-five minutes and amount to a real climb, so a reasonable level of fitness helps. The well takes its name from a medieval comparison with the legendary cave of Saint Patrick in Ireland, an entrance to purgatory. It can become busy and slow when groups bunch on the stairs, so early morning before the coach parties arrive is the most comfortable time. The well lies at the top of the funicular from Orvieto's railway station, an easy first or last stop on a visit to this hill town in southern Umbria.