The smallest of the five bronze doors leading into the Basilica di San Pietro is known as the Porta Santa (Holy Door). The work of Vico Consorti, the door was consecrated and opened on December 24th, 1949, by Pope Pius XII (r. 1939-58), marking the start of the Jubilee, or Holy Year, of 1950.
The Porta Santa is made up of sixteen bronze panels, which depict scenes inspired by the theme of the 1950 Jubilee, 'The great return and the great pardon'. There are scenes of sin, incredulity and denial, but also of reconciliation between man and God. The bottom right panel depicts Pope Pius XII opening the Holy Door.
The Porta Santa is only used on the occasion of a Jubilee, which is normally held every twenty-five years; for the rest of the time the portal is bricked up on the inside. At the start of a Jubilee the bricks are removed and the door is officially opened by the pope, who strikes it with a silver hammer. The Holy Father then uses the door to be the first to enter the basilica, and, at the close of the Jubilee, he is the last person to leave through it.
During the course of a Jubilee the Porta Santa remains permanently open; at the close of the Holy Year the portal is once again bricked up.