Vatican City  - Pope Benedict XVI was scheduled Wednesday to lead the Vatican's Christmas festivities by celebrating the traditional midnight Mass.

Earlier, the 81-year-old pontiff appeared briefly from a window overlooking St Peter's Square to light a candle symbolizing Peace.

Benedict's gesture followed the unveiling in the square of a Nativity Scene, or crib, that recreates the scene of Jesus' birth.

This year's model - the Vatican revived the custom in 1982 - is inspired by St Luke's Gospel account of Christ's nativity taking place in humble surroundings on the outskirts of Bethlehem.

The story narrates how Jesus' mother, Mary, and foster father Joseph, unable to find lodging, seek a manger for shelter - in the model, a stall covered with wooden planks.

A watchtower set in the city "walls of Bethlehem," described in Luke's Gospel, provide the backdrop, while a pastoral scene has been recreated to the right of the stall, including statues of shepherds. To the left, simple dwellings, including a bakery, are shown.

Several of the statues, some of them larger-than-life-size, were created in 1842 by St Vincent Pallotti for a crib in the Sant'Andrea della Valle church in Rome.

The Nativity Scene stands next the Vatican's Christmas tree - this year a 33-metre high spruce from Austria.

Benedict has encouraged Catholics to display their own nativity scenes and Christmas trees, both "spiritual" symbols representing Christ's appearance on Earth, according to the German-born pontiff.

The Vatican's Christmas Eve festivities are set to culminate with the midnight Mass, including Benedict's homily, while on Thursday the pontiff planned to deliver his Christmas Day blessings and traditional Urbi et Orbi message. (dpa)