St Paul's south side, facing the Millennium Bridge, has been unveiled following extensive restoration work.
The south transept faces the Millennium Bridge
Views of the cathedral's south transept had been obscured by scaffolding for several months while it underwent £4.2m worth of cleaning and repairs.
The work is part of a £40m campaign to restore Sir Christopher Wren's masterpiece to its former glory.
The project is due to be completed in 2008 to mark the 300th anniversary of the London landmark's completion.
Cathedral supporters said more funds were needed to continue the work and improve facilities for visitors.
Nigel Kirkup, of the St Paul's Foundation Trustees, said: "We are so grateful to donors both large and small, and in particular the Corporation of London, for making this next phase of the project possible.
"It is wonderful to see the South Transept restored to its former glory.
"So far, nearly £37m has been raised to clean and restore the whole of St Paul's, but we still need further support to ensure that all the necessary work can be finished in time for the 300th anniversary in 2008."