From the Guardian:
It has been called “the most influential painting ever” and “the world’s most coveted masterpiece”. It is also the most frequently stolen. And now, after a four-year restoration to clean away six centuries of dirt and varnish, the Ghent Altarpiece looks the way it did originally – electric, radiant, gorgeous and glorious.
The altarpiece, also known as The Adoration of the Mystic Lamb, was unveiled in St Bavo’s Cathedral, Ghent, today. The work, in its entirety or just in part, has been stolen six times, and found itself at the centre of no fewer than 13 crimes and mysteries, several of which remain unsolved – until now, that is, thanks to the restoration.
The altarpiece was likely begun by Hubert van Eyck in 1426, but he died that year so there has always been a question over whether any of his hand survives in the work. It was completed by his younger brother, Jan, and rapidly became one of the most famous artworks in the world, a point of pilgrimage for educated tourists and artists, something it continues to be today.
More, including illustrations, at the link.