On Good Friday there is a Papal Mass at the Vatican in Saint Peter's Basilica at 5PM. In the evening the ritual of the Stations of the Cross, or Via Crucis, is enacted near Rome's Colosseum, usually starting at 9:15PM. The stations of the Via Crucis were placed at the Colosseum in 1744 by Pope Benedict XIV. A huge cross with burning torches lights the sky as the stations of the cross are described in several languages. At the end, the Pope gives a blessing. This is a very moving and popular procession. If you go, expect big crowds and be aware of the possibility of pick-pockets as you would in any very crowded tourist place.
Papal Mass and Easter Vigil are held on Holy Saturday at 9PM in Saint Peter's Basilica.
To check for updated times and information go to the Calendar of Vatican Liturgical Celebrations