The British Library in London has been given Grade I listed status for its “outstanding architectural and historic interest.” The distinction places the library under statutory heritage protection, preventing it from being demolished, extended, or altered without special permission.

Completed in 1998—with a nine-year delay and going $546 million over budget—the building is one of the youngest in the UK to have been granted heritage protection.

But the building wasn’t always so highly regarded. Designed by architects Sir Colin St John Wilson and his partner, MJ Long, the library was once referred to by a parliamentary committee as “one of the ugliest buildings in the world.”

It is estimated that today the library houses around 14 million books across its five floors and 11 reading rooms. It includes treasures such as the Lindisfarne Gospels, William Shakespeare’s First Folio (1623), Gutenberg’s 1455 Bible, and a hand-written copy of George Frideric Handel’s Messiah (1741).

British Library chief executive Roly Keating praised the building for its “courageous and visionary design.”

“Even in the relatively short period since its opening, it has worked its way into the affections of millions of visitors and researchers, who have discovered its beautiful spaces, subtle use of natural light and exquisite detailing,” he told the BBC.

“As well as celebrating architectural excellence, this listing is a reminder, in the midst of the digital age, of the vital importance of libraries as physical spaces of the highest quality at the heart of their communities,” Keating added.

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