The BBC's Alva McNichol: "The task now is to keep it clean"

The Pope toured Saint Peter's Square, while Italian President Carlo Azeglio Ciampi and foreign diplomats to the Holy See and Italy watched the ceremony.

A full orchestra accompanied the singing of the Te Deum, before the festivities ended with a light show and fireworks.

"Pilgrims coming to Rome from all over the world will be able to relive the experience of earlier pilgrims, enchanted by this basilica's magnificent and imposing structures," the Pope said.

The Pope's outdoor audience in front of the newly restored St Peter's Basilica on Wednesday

"These restoration works must remind us that it is for all of us to make a courageous revision of our life on the occasion of the jubilee."

He thanked the managing director of Italian oil giant ENI, which sponsored the refurbishment.

It has taken $5 million and almost three years of scrubbing and cleaning to remove the stains of atmospheric pollution from the nearly 400-year-old facade of St Peter's - one of the masterpieces of early Baroque architecture.

Air quality

Now the scaffolding, which has enveloped the major church of Christendom for two summers, has been removed and Carlo Maderno's architecture has been revealed in its full glory.

Some of the colours added to the travertine marble facade in the 18th Century - tints of green and red - are now visible for the first time.

Restorer Vittorio Giacomelli says the restored Basilica is closer to the original building

An analysis of the quality of the air around St Peter's shows that it is heavily polluted by the hundreds of tourist buses which bring pilgrims to the Vatican.

The pollution is expected to get worse during jubilee celebrations which will bring tens of millions of visitors to Rome during the coming year.

Protective coatings have been applied to parts of the stonework to try to limit future damage.

Specialists used the latest engineering techniques to ensure that the facade resembles as closely as possible its original colouring.

Vittorio Giacomelli, the expert who led the restoration, said he thought it would take many decades before similar work was necessary.