AP Photo/Gregorio Borgia

Pope Benedict XVI lights a candle at his studio window overlooking St. Peter's Square at the Vatican, after the unveiling of the Nativity scene, Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

The dome of St. Peter's Basilica, center, is framed by a Christmas tree at the Vatican Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

A Vatican security officer stands by the Nativity scene that was unveiled in St. Peter's Square at the Vatican Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

People watch and take pictures of the Nativity scene that was unveiled in St. Peter's Square at the Vatican, Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

People watch and take pictures of the Nativity scene that was unveiled at the Vatican, Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

A Vatican security officer stands by the Nativity scene in St. Peter's Square that was unveiled at the Vatican Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

Pope Benedict XVI lights a candle at his studio window overlooking St. Peter's Square at the Vatican, after the unveiling of the Nativity scene, Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.

AP Photo/Gregorio Borgia

Pope Benedict XVI holds a candle at his studio window overlooking St. Peter's Square at the Vatican, after the unveiling of the Nativity scene, Monday, Dec. 24, 2012. Pope Benedict XVI has lit a Christmas peace candle set on the windowsill of his private studio overlooking square. Pilgrims, tourists and Romans gathered below in St. Peter's Square for the inauguration Monday evening of a Nativity scene and cheered when the flame was lit. Later, he will appear in St. Peter's Basilica to lead Christmas Eve Mass.