It is the sometimes secret, subterranean world which even many who have lived in Norwich their whole lives are unaware of.

Eastern Daily Press: Inside the Jurnet’s Bar on King Street, Norwich. Picture: Jamie HoneywoodInside the Jurnet’s Bar on King Street, Norwich. Picture: Jamie Honeywood (Image: Jamie HoneywoodArchantNorwichNorfolk)

Medieval buildings such as Dragon Hall, The Guildhall and Strangers Hall are beloved landmarks, but what lies beneath some of the city's buildings is considerably less familiar.

But Norwich boasts at least 80 undercrofts - the majority of dating from the 15th century.

The story of the them is told in the latest Aspects of Norwich publication produced by civic watchdog The Norwich Society.

Terry George, who has visited more than 50 of the city's undercrofts, says they are defined as vaulted rooms beneath the main room of a medieval house, wholly or partly under the ground.

Eastern Daily Press: Terry George at The Guildhall undercroft. Picture by SIMON FINLAY.Terry George at The Guildhall undercroft. Picture by SIMON FINLAY.

He said: "Undercrofts were commonly built throughout the 13th, 14th and 15th centuries.

"Most were built of stone, although Norwich is the exception with nearly all being built of brick, probably because of the shortage of stone in and near Norwich.

"Norwich has the largest collection of medieval undercrofts in the country and there were probably more than a hundred at one time or another."

Most are beneath domestic buildings, but some are under civic or ecclesiastical buildings, such as The Guildhall, St Andrews Hall and the Bishop's Palace.

Eastern Daily Press: The Undercroft beneath the Assembly House, Norwich. Photo: Terry George.The Undercroft beneath the Assembly House, Norwich. Photo: Terry George. (Image: Terry George.)

Some would have been used as storerooms, but others would have been rented out as shops. The one beneath The Guildhall was probably a prison right from the start.

One of the oldest, dating back to the 12th century, is under Wensum Lodge in King Street and is home to Jurnet's Bar.

Other examples can be found under the Bridewell, The Assembly House, Dragon Hall, Curat House (now Fat Face), Zelley's in St Giles Street, Bedford's and Louis Marchesi.

While most are not generally open to the public, guided tours are often arranged during Heritage Open Days.

Mr George said: "Any apparent lack of public interest in this fascinating part of our local history often springs from a lack of awareness of these subterranean treasures, rather than indifference to their local heritage."

The Aspects of Norwich publication is available for £3.50 by contacting admin@thenorwichsociety.org.uk