The building was discovered when exploratory pits were dug
Archaeologists digging at a cathedral in Kent have unearthed evidence of a previously unknown building.
An excavation project was started at Rochester Cathedral to conserve a Roman city wall.
While digging exploratory pits, experts came across a medieval structure believed to be a window or a door of a building not discovered before.
It is hoped the find could provide information about how the whole area functioned more than 600 years ago.
Archaeologist Graham Keevil said: "We know about the cathedral and the way that developed.
"We know a bit about the cloister where the monks who worked in the cathedral went about their everyday lives.
"But everything else that goes on in the precinct we really do not know very much about.
"So to get a major building like this, even from such a relatively small pit, the implications of that window or door are massive in terms of then our understanding of the entire precinct."