John Paul II brought an important rock 'n' roll lesson to the Vatican -- you've got to take your show on the road. The first non-Italian pope in 450 years celebrated his 20th anniversary in the Holy See Friday with 20,000 fellow Poles, who had made a pilgrimage to the Vatican for the occasion. The papal encyclical he signed Thursday confirmed his status as a pontiff deeply engaged with the secular ideas of his time, but his legacy will run a lot deeper: "John Paul II created the idea of a world church for the modern world by virtue of his extraordinary travels," says TIME religion correspondent David Van Biema. "After centuries in which it seemed as though the papacy might have been out of touch with the ways of the modern world, he has made use of those ways to give Catholicism a new face -- he's a media pope for a media age." And as he continues to engage vigorously with a fast-changing world in his 79th year, the College of Cardinals knows better than most that John Paul II will be a hard act to follow.