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A popular venue for weddings, King's College Chapel is at the heart of the medieval university in the cobbled streets of Old Aberdeen. It is topped by the Crown Tower, voted the nation's third most "treasured place" in a recent competition run by the Royal Commission on the Ancient and Historical Monuments of Scotland, and has now been restored to its former glory.

The tower was built in 1504 but toppled by a gale in 1663 which sent masonry crashing through the chapel roof. It was reconstructed after an appeal for funds, with the help of a grant from the town council. The inscription of the master mason George Thomson can still be seen.

The recent restoration was carried out in 2004 by Acanthus Architects Douglas Forrest, Laing Traditional Masonry and the university's estates team (supported by the Aberdeen City Heritage Trust). The key principle was a return to original materials. Where the tower had been repointed with hard-setting cement, this was stripped out and replaced by lime mortar, in common use until the end of the 19th century, which can "breathe", take in moisture and protect the stone.

Suggestions for this architectural treasures series are welcome: matthew.reisz@tsleducation.com.