Description:Thousands pack St. Peter's Basilica in Rome to witness history. Pope Benedict 16th presided over the Ash Wednesday observance, in what was his last scheduled Mass as Pontiff. The capacity crowd gave the Pope a thunderous ovation lasting several minutes, and in an unusual gesture, bishops took off their caps in a sign of respect. A visibly moved Pontiff thanked the audience, adding "Now, let's return to prayer".(1:26)