How Many People Are in This Painting? The Prado Museum Is Using A.I. to Find Out

As legend has it, the young woman who would become St. Ursula set out from her native England in the fourth century to journey across the European continent. The reasons for her travels—whether to marry a man at her father’s behest or to undertake a pilgrimage to Rome—are hazy. But one vivid, if unlikely, detail has endured: Her traveling companion...