The ancient window has been described as the English equivalent of the Sistine Chapel.
The fixture is the biggest medieval stained glass window in Europe, at 24 metres tall, and the size of a tennis court, with 311 panes.
Millions of pounds have been spent on fixture positioned at the East Front of the building which was originally created in 1408 by glazier John Thornton.
Of the 108 major panels in the East Window, 81 illustrate scenes from the last book of the New Testament -The Book of Revelation (Apocalypse) - which describes, sometimes in graphic detail, the end of the world.
It is thought John Thornton had access to Royal illuminated manuscripts which contained images from the Apocalypse, a mark of the ambition and scale of the project in its day.
The window has been restored with the help of senior conservator at York Glaziers Trust, Nick Teed. It is part of a five-year project supported by a £10.5 million grant from the Heritage Lottery Fund, and is the lagest conservation project of its kind in the UK.
The stonework is also being renewed, with the project due to be completed in 2018.
