LONDON (AP) — A facelift that restored London’s 166-year-old Big Ben clocktower to a sparkling shine was nominated Thursday for Britain’s leading architecture award.

The RIBA Stirling Prize committee said the five-year refurbishment of the tower at Parliament is “a veritable masterclass in conservation and craftsmanship” that preserves a “defining symbol of British heritage.”

The 96-meter (316-foot) structure, formally known as the Elizabeth Tower, houses Big Ben, the giant bell whose bong has sounded the hours since 1859.

It fell silent in 2017 when the tower was covered in scaffolding for repairs. The original cost estimate of 29 million pounds ($39 million) more than doubled, but the renovation unveiled in 2022 has been widely praised.

As well as repairing the corroded cast-iron roof and damaged stonework, craftspeople returned the clock to its original blue and gold color scheme after decades of being painted black.

The repair work used traditional materials and skills in stonemasonry, gilding, glass cutting and clockmaking, though some modernizations were made, including replacing lightbulbs behind each clock face with energy-efficient LED bulbs. Workers also installed an elevator as an alternative to the 334 steps up to the belfry.

The Stirling Prize, organized by the Royal Institute of British Architects, usually goes to a new building, though last year’s winner was a railway project, London’s Elizabeth Line.

Other contenders this year include pharmaceutical company AstraZeneca’s new Discovery Center in Cambridge, the London College of Fashion in east London and three housing developments.

The winner will be announced Oct. 16.