Saint Helen was the mother of the first Christian Emperor, Constantine. The 'Golden Legend' says that she found the cross on which Christ had been crucified, known as the True Cross.
The Cross had been buried underground for over two hundred years but was rediscovered because of sweet-smelling perfumes coming from the ground. When the ground was opened, three crosses were found. In order to determine which was Christ's cross, each one was held up before a woman who was close to death. When the True Cross was held before her, she opened her eyes and was cured.
The Cross performed many other miracles, and pieces of wood reputed to have come from it have since been treasured in reliquaries across the world.