Archaeologists have discovered a 1,000-year-old church during construction work at Lincoln Castle.
Eight skeletons have also been found in the building – which was never known about until now – by workers on the £19.9m Lincoln Castle Revealed project.
Experts believe the church pre-dates both the castle and the Norman conquest – and is one of the most important archaeological finds in Britain.
Cecily Spall, an archaeologist on the site, said the amazing find was hugely significant for Lincoln.
“The information we can get from this undocumented church is gold dust,” she said.
“Historical documents only tell part of the story for this area so this find is very special.”
The skeletons will be sent to human bone specialists to ascertain the age, sex and medical history of them.
They will then go on display at The Collection museum.
“It is really exciting. I never expected to find anything like this in my career.
“It is without doubt one of the most historically significant things we have found.”
Another skeleton was found wrapped in a finely woven material within the wall foundations during excavations for a lift shaft.
This may be the relics of a holy person placed inside the wall to dedicate the building.
A limestone coffin with a lid mortared in place has also been found in a three by three metre trench, three metres below today’s ground level.
Miss Spall has used an endoscopic camera to look inside the coffin and there is a perfectly preserved skeleton within.
“The skeletons are in the right alignment for Christian burials and along with a floor surface being present this indicates a church having been here,” she added.
“All the burials are high status people. Some were in wooden coffins and one was in a cloth which all indicates significant social status at the time of burial.
“We assume that the church was about seven metres by four metres and if that is right, the sarcophagus would be right in the middle of the building which is the most important place to be buried.
“We have also found tenth century pottery so the building and burials are likely to be from the tenth century and pre-date the castle by some 100 years.”
The Lincoln Castle Revealed project will see the creation of a purpose-built Magna Carta centre and free entry to the castle grounds and should be completed by 2015.
Emma Tatlow, Visit Lincoln Partnership manager, believes the find presents a unique opportunity to attract visitors to the city.
“This is going to create lots of coverage for Lincoln,” she said.
“It is a wonderful opportunity to shout about Lincoln and what is here and attract people to the city.
“It is a great marketing opportunity.
“Putting the skeletons on display at the Collection is a brilliant idea as it allows people who are interested to actually see what has been discovered.”