Contractors working on the restoration of Delapre Abbey have discovered a Victorian plunge pool.
The £7.2 million refurbishment project, funded by the Heritage Lottery Fund and Northampton Borough Council, since March last year.
The abbey started life as a Cluniac nunnery in the twelfth century and has served many different purposes since.
The Delapre Abbey Preservation Trust has been working alongside the borough council and specialist contractor Robert Woodhead Heritage to conserve the beautiful architecture.
And as part of their excavations to the north of the main building, they discovered the plunge pool.
Joe Prentice, archaeological building specialist working with Iain Soden Heritage Services, said: “At first we were confused about what it was because of the shape and size of it, but then we had a eureka moment.
“By the time you reach the late 19th century, places like Delapre had plumbing, which meant they could have these kinds of baths.
“Also in the late 1800s – perhaps the 1880s or 1890s – into the period just pre-war, there was a bit of a fad for healthy living, and a belief in the healing effect of plunging into cold water.”
The Delapre Abbey café and Billiard Room conversion is expected to open in November 2016 with the remainder of the building opening in February 2017.
This will be the first time the abbey has been open to the public in its 900-year history. It is estimated that there will be around 40,000 visitors a year.
DAPT director, Rachael Boyd, said: “This is another exciting find at Delapre which adds to our understanding of the house, its use and development over the years.
“We look forward to sharing these many different stories with the public when the house opens in February 2017.”