Why do we celebrate the Exaltation of the Holy Cross?

As well as celebrating the sacrifice of Jesus on the Cross, the feast of the Exaltation of the Holy Cross commemorates two historical events. The first is the discovery in 320 AD of the True Cross, of Calvary and of the tomb of Christ by St. Helena, the mother of Emperor Constantine, which the Romans had buried under a Temple to Venus. The second is the dedication of a church on the site in 335 AD. Today this church, in continuous existence since then, is known as the Basilica of the Holy Sepulcher, and houses Calvary, the Tomb of Jesus and the cistern in which St. Helena found the instruments of the Passion, including the Cross.