On the summit of Mont Voutois, facing the ancient town of Tonnerre, the Abbey of Saint-Michel was founded in the 5th century. Completely ruined by the Norman invasions, it was restored in the 10th century. Saint-Thierry, who was passing through, died here and became the town's patron saint. On the eve of the French Revolution, the abbey was a shadow of its former self. It was sold as national property. All that remains of the medieval buildings are two vaulted rooms.