Cathedral of St. Gatianus, Tours, France (12-15th c.)
Stained Glass windows showing scenes from the life of St. Martin.
According to the early 5th century hagiography of Sulpicius Severus, Martin came upon a group of pagans who worshipped at an altar next to a sacred tree. After destroying the shrine, he offered to demonstrate the power of his God by standing beside the tree as it was cut down (or he was made to stand there by the upset pagans, take your pick). In any case, as the tree fell, he made the sign of the cross and the descent was miraculously altered, so that the tree nearly landed on the gleeful pagans. Awed by this miracle, the entire group converted on the spot.