Orvieto

Orvieto stands on a plug of volcanic tufa rising sheer above the plain, and the Etruscans and everyone after them dug into it — around twelve hundred caves, wells, quarries and dovecotes run under the streets. The cathedral's striped façade took three centuries, and St Patrick's Well is a double-helix staircase of 248 steps, designed so that mules could descend and ascend without meeting.