Poher is an ancient principality that emerged in the Early Middle Ages in Cornouaille in west-central Brittany. Its capital was the Gallo-Roman city of Vorgium, capital of the Osismii, which became Carhaix after the fall of the Roman Empire. Archaeological excavations scheduled since 1999 show that, even if the city lost its function as capital after the 4th century, it was nonetheless a stronghold and major strategic crossroads.