Rare stone carvings that had been hidden for centuries were found in a bishop's tomb in Scotland's ancient Dunkeld Cathedral.

During a routine inspection, conservationists reportedly found at least a dozen unrecorded carved figures on the back of Bishop Cardeny's tomb, which was created in 1420.

The conservationists used torches and mirrors to find them and the carving images allowed them to do in-depth analysis with 3-D photogrammetric technology, reports Christian Today.

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Officials with Historic Environment Scotland led the discovery.

"The discovery of these rare, hidden carvings behind the 15th-century tomb of Bishop Cardeny is very exciting and will enrich our understanding of the history of Dunkeld Cathedral and late medieval stone carving," Colin Muir, a stone conservator at HES, told the publication.

Cardeny was the cathedral's longest-serving bishop and was appointed by Pope Benedict XIII in 1399.

"This discovery also gives fresh incentive for further research and exploration of the site, as we still don't know when exactly the tomb was moved, or why," said Muir. "This discovery also hints that there may still be other obscured areas of detail preserved within the walls behind the tomb."

The cathedral itself was developed over a period of about 250 years, with the earliest surviving section dating from the late 1200s, according to the BBC.