Experts believe they have uncovered the tomb of England's King Edward the Confessor in Westminster Abbey.
The tomb is under the mosaic floor at Westminster Abbey
Archaeologists using radar have also discovered a series of royal tombs dating back to the 13th and 14th centuries in under-floor chambers.
The discoveries were made as experts investigated the construction of the Abbey's 13th-century mosaic pavement.
Consultant archaeologist Dr Warwick Rodwell said it was "of historical interest unparalleled anywhere else".
Dr Rodwell worked with expert Erica Utsi using high-frequency radar to look down to a depth of about 20 inches.
"Little did we expect that, lying beneath, we would find chambers, vaults and foundations... dating back to the very founding of the Abbey, over a millennium ago.
"We have never been able to locate the original tomb of Edward until now," he said.
"The Victorians tried to find out more about what tombs were under here, but they simply did not have the technology to do it.
"The mystery around the location of his crypt has been running for many years. Every day brings us new insights and new facts."
Edward reigned from 1042 to 1066 and was Patron Saint of England until 1415, when he was replaced by Saint George.
He was the first Sovereign to develop the custom of touching his people to cure them - a tradition that continued for nearly 700 years to the time of Queen Anne.
Further investigations are being carried out to establish more facts about the location, purpose, history and content of the main tomb and other chambers, graves and coffins.