The first renovated face of St Paul's Cathedral is being revealed to the public on Wednesday.
The East End of the cathedral took 13 months to clean
A total of £500,000 was spent on cleaning the East End side as part of a £40m restoration plan.
The programme will see the entire cathedral in the City of London repaired for the 300th anniversary of the laying of the final stone in 1708.
A special cleaning process was undertaken by the cathedral's own team of stone masons over 13 months.
The first restoration phase was completed in February 2002 when work on the interior south transept stripped away centuries of dirt to reveal the natural cream colour of the walls' Portland stone.
Restoration to the interior should be completed by early 2005.
Work on the exterior West Front, which includes rebuilding the West Steps, has been funded by a £5m donation from the late philanthropist billionaire Sir Paul Getty.
An anonymous donation has funded the East End project .
The plan is for the south side and then the north side to be renovated and funding is currently being sought for those two projects.
The Dean of St Paul's, the Very Reverend Dr John Moses, said: "Every one of us at St Paul's is delighted with the work that has been carried out by our own masons in completing the first phase of restoration and stone cleaning at the East End of the cathedral.
The cleaning removed dirt and sulphate deposits
"The generosity of the donor and the skill of the masons have enabled us to see more clearly the warmth of the stone, the delicacy and strength of the carving.
"It is a fine achievement."
Sir Christopher Wren was commissioned to design St Paul's in 1668, two years after the Great Fire of London destroyed the original cathedral.
After delays because of problems with the architect's plans the building was finally completed in 1708.
Parliament officially declared St Paul's open in 1710.