Pope Benedict XVI expressed his hope that the 23rd World Youth Day would act as a new upper room from which the young pilgrims would leave filled with the fire of the Holy Spirit ready to proclaim the risen Christ.

Speaking to the young pilgrims from around the world at the Papal "final" Mass which was the culmination of the World Youth Day events today, Pope Benedict called upon the young to open their hearts to the Holy Spirit and be like the Apostles at Pentecost.

As sunlight streamed down on the hundreds of thousands of youngsters who have spent the week in Sydney-EWTN estimated some 600,000 souls-the Holy Father said that the days in Australia had shown the Church as it really is.

He said: "Our eyes have been open to see the world all around us truly as the poet says charged with the grandeur of God filled with the glory of his creative Love. Here too, in the presence of young Christians from all over the world we have a living experience of the Spirit's presence and power in the life of the church.

"We have seen the church for the one thing she truly is: the body of Christ, a living community of love, embracing people of every race, nation and country of every time and place in the unity borne of our faith in the risen Lord.

"The power of the spirit never ceases to fill the Church with life. Through the grace of the Church's sacraments the power also flows deep within us like an underground river which nourishes our spirit ...and to the source of our true life which is Christ."

Emphasising the importance of daily prayer he said that the Grace of the Spirit was not something that could be merited or achieved but that we can "only receive as pure gift. "

He said: "God's love can only unleash its power when he is allowed to change us from within. We have to let it to break through the hard crust of our indifference .. our blind conformity to the spirit of this age. Only then can we let it ignite our imagination and shape our deepest desires."

Speaking of the martyrs and missionaries who had given their lives to transmitting the faith, he asked the young people what they were passing on to the next generation.

Pope Benedict asked: "Are you building your lives on strong foundations, on something that will endure? Are you building your lives in a way that opens up space for the spirit in the midst of a world that wants to forget God, rejects him in the name of a falsely conceived freedom? How are you using the gifts you have been given, the power which the Holy Spirit is even now prepared to represent within you?

"What legacy will you leave to young people yet to come? What difference will you make?

"The power of the Holy Spirit does not only enlighten us and console us, it also points us towards the future, to the coming of God's Kingdom. For the magnificent vision of humanity redeemed and renewed we see in the new age promised by today's Gospel. "St Luke tells us that Jesus Christ is the fulfilment of all God's promises, the Messiah who fully confesses the Holy Spirit in order to bestow the gift upon on all mankind. It is the outpouring of Christ's spirit on all humanity is a bridge of hope and deliverance from everything that impoverishes us.

"It gives the blind new sight, it sets the downtrodden free, it gives unity in and thru diversity. This power can create a new world it can renew the fires of the earth..."

A new generation of young Christians is being called to build the new age, Pope Benedict said.

The Holy Father said: "The world needs this renewal. In so many of our societies, side-by-side with material prosperity, a spiritual desert is breeding an interior emptiness, an unnamed fear, a quiet sense of despair.

"How many of our contemporaries have filled broken and empty systems in a desperate search for meaning, the ultimate meaning that only love can give and this is the great and liberating gift that the Gospel brings. It reveals our dignity as men and women created in the image and likeness of God. It reveals humanity's sublime calling which is to find fulfilment in love. It is close to the truth about men and about life.

"The Church also needs renewal. She needs your faith, your idealism, your generosity so that she can always be young in the Spirit."

After the Holy Father's homily, the pilgrims at the racecourse fell silent for a few minutes, before the Pope presented the Sacrament of Confirmation on 24 young catechumens from around the world.

During the Mass, which was celebrated in a number of languages, including Latin, the Pope prayed the Angelus, reminding the young people of Our Lady's great affirmation of Christ on behalf of all of humanity.

At the end of the Mass the Pope announced that the next World Youth Day in 2011 will take place in Madrid.

"Until then, let us continue to pray for one another and continue to bear witness to Christ. May God bless you all," he said.