Under the village of Saint-Émilion there’s a church that nobody built. They dug it.
Around the late 11th or early 12th century, someone started carving it out of the limestone to honour Émilion, an 8th-century Breton hermit, and to host the pilgrims visiting his tomb. About 15,000 m³ of rock came out: three naves, monolithic pillars, some 38 m long and 11-12 m high. It’s the largest underground church of its kind in Europe, still consecrated, guided visits only.
Then came the Revolution. In 1793 it was sold off and turned into a saltpetre factory for gunpowder, and most of its decoration disappeared. On the Last Judgement tympanum of the portal, the saints have no heads: knocked off by revolutionaries.
It wasn’t a local whim. Beheading statues was a standard anti-royal, anti-clerical gesture. The famous case: the 28 kings on the façade of Notre-Dame de Paris, kings of Judah mistaken for kings of France. In 1977, building works in a Paris mansion turned up 364 fragments, 21 of them heads. They’re in the Musée de Cluny now.
https://fr.wikipedia.org/wiki/%C3%89glise_monolithe_de_Saint-%C3%89milion