Media playback is unsupported on your device Media caption Take a tour of the castle that was 'lost' for 250 years

A 17th century castle "lost" for more than 250 years has been rediscovered in the centre of a town on the Irish border.

An archaeological excavation in Clones, County Monaghan, had failed to uncover the remains of the castle.

But, unknown to the experts the walls of the four-storey building were still standing nearby.

The walls were covered in ivy and hidden in undergrowth but there were clues that had been overlooked.

Image caption The castle had remained hidden for more than 250 years

It was found behind a Georgian terrace known as Castle Street, which contains a building called Castle House.

Monaghan county heritage officer Shirley Clerkin said it shows "when you start opening your eyes, looking afresh at things, you can rediscover really, really interesting buildings".

She said although the castle was hidden in plain sight, no one had been really looking for it.

Image caption Shirley Clerkin and George Knight came across the building a few months ago

"There had been an excavation done in a southerly direction from here looking for the castle as part of a commercial dig but they didn't really find any upstanding remains and then we assumed there was no castle here," she said.

'Significant'

She came across the building a few months ago along with local historian George Knight when they explored an area just a few metres away from the Diamond in the centre of the town.

"We crossed over a lot of barbed wire, a lot of brambles, woody-stuff and we came in front of this building and looked up at the front wall and realised we were standing in front of something potentially very significant," she said.

Image caption George Knight said he was aware the building existed but experts had previously dismissed it "with a cursory glance" as being "of no great historical importance"

"This building had been re-used as an agricultural building and had been completely forgotten about from the point of view of it being a potential castle candidate.

"I think there was probably a wee bit of folklore around it - kids maybe played here when they were young and pretended it was a castle and they were absolutely right, it is a castle."

Image caption The site had been used as a rubbish dump for many years

George Knight said he was aware the building existed but experts had previously dismissed it "with a cursory glance" as being "of no great historical importance".

"It has been used as a rubbish dump for many years. The joists carrying the first floor, only one is still in place the rest have collapsed down," he said.

Image caption The fortified house is thought to have been built in the 1600s by the local landlords

"We think the original slate roof has probably collapsed down into the building as well."

The fortified house is thought to have been built in the 1600s by the local landlords, the Lennard-Barret family, who may only have lived in it for 50 years until the outbreak of the Jacobite wars in 1688.

Media playback is unsupported on your device Media caption How did the castle stay hidden for 250 years?

'Historical depth'

It is shown on a 1741 drawing of Clones in the collection of the National Library in Dublin along with the town's other historical landmarks.

"Clones has a lot of historical depth to it We already have early Christian sites here, we have an Augustinian abbey, a motte and bailey from Norman times and this is the next piece of the jigsaw," Shirley Clerkin said.

Image caption Only one of the joists carrying the first floor remains in place

"We have what we believe here to be a remnant of the plantation castle that we can see on the 1741 drawing.

"It means that Clones really has got little bits of every period in Irish history upstanding in the town."

Local volunteers have been cutting back some of the undergrowth to reveal more of the building, including the musket slits, fortified door, corbels and wooden floor beams.

Image caption The fortified house is thought to have been built in the 1600s by the local landlords

An open day has been held for people to come and see the castle and learn more about its history.

Archaeologists will return to Clones to carry out excavations involving the local community to see what other artefacts can be unearthed.

Preservation

George Knight said the discovery has become the talk of the town and people were keen to learn more about the history hidden on their doorstep.

"It really is a missing link in the story of Clones, a unique building and something that we're very keen to preserve for future generations," he said.

Image caption Shirley Clerkin is convinced that there are more discoveries to be made

"We hope that any artefacts found will remain here in Clones and the building and the artefacts associated with it will tell the full story and the history of what happened within these walls."

Shirley Clerkin is convinced that there are more discoveries to be made.

Image caption Hidden history - a staircase leading into the castle

"I think this place has got unlimited potential," she said.

"We already have two tunnels, we have one under the staircase here and we have one in the wall outside and there's lots of legends of tunnels in Clones, so I think maybe this is one of those little links and it's a tantalising glimpse of the past."