Basilica of Aquileia

Aquileia was one of the largest cities of the Roman Empire—a strategic Adriatic gateway that Attila the Hun destroyed in 452. Its basilica, begun under Bishop Theodore right after Constantine legalised Christianity in 313, preserves a 760-square-metre floor mosaic, the largest early Christian pavement in the Western world. Buried and forgotten beneath later flooring, it was rediscovered only in the early 20th century, revealing scenes of the story of Jonah, fishing putti, and a rich bestiary. The adjoining crypt and 11th-century campanile testify to the city's long importance as a patriarchate. Today the sleepy town belies its past as a metropolis that rivalled Rome itself.