Quoting (and translating) the Michelin Guide Vert for the Auvergne region: "The church at Saint-Menoux is without doubt one of the most beautiful in the Bourbonnais. The existing edifice was built in the second half of the 12th century on the site of an old sanctuary dedicated to the memory of a 7th century Breton monk of Irish origins whose name was Menulph."
Menulphus is described elsewhere as an Irish bishop who died in the Bourbonnais province in the 7th century. After Menulph's death, his simple-minded manservant, Blaise, not understanding that Menulph was really dead, poked a hole in Menulph's sarcophagus and stuck his head inside to say a final goodbye to him. When he pulled his head back out his simple-mindedness had been cured. The cure was attributed to Menulph as the final miracle he ever performed.
Since that time, Saint-Menoux has been a pilgrimage destination known as a place where the simple-minded can find a cure... as long as their head doesn't actually touch the stone of the sarcophagus, because in that case their condition gets worse rather than better. If you're only slightly simple-minded, you might not want to take the risk.
The church at Saint-Menoux, like most, has been maintained, modified, improved, and expanded over the centuries to become what it is today. It stands less than 10 minutes north of Souvigny by car, and about the same distance east of the spa town of Bourbon-l'Archambault.