There are plenty of drumlins in County Down - but have you heard of the Mound of Down?
If not, that is probably because it has been hidden from public view by trees and gorse for decades.
But work is now under way to expose this fortification which could be about 1,000 years old.
Tim Campbell, director of the St Patrick Centre in Downpatrick, said it was one of the largest megalithic hill forts in western Europe.
"We have forgotten about it as it been overgrown with trees," he said.
"It was the seat of the high kings when they moved from the Navan area of Armagh eastwards.
"It is a very important site and perhaps in the very reason Down is called Down, Down from Dun - the big fort."
The enclosure is defined by a massive bank and ditch that encircles what was once a drumlin island in the Quoile Marshes.
Although the site has yet to undergo archaeological excavation, it is thought that the large earthwork on the mound is a pre-Norman fortification.
It is most likely to be a royal stronghold of the Dál Fiatach, the ruling dynasty of this part of County Down in the first millennium AD.
Ken Neill, an archaeologist for the Environment Agency which is working to control the vegetation at the site, said it dated back to the Iron Age, or the early Christian period.
"It occupies a site the size of four football pitches and sits in a very strategic position in the Quoile Marshes, because, in the past especially, it must have been surrounded by water at least part of the year," he said.
"If you were attacking it, you had to get down into the ditch and then you've got this huge bank standing in front of you.
"If you can imagine people lining the top of it trying to stop you - it must have been quite an obstacle."
MP for South Down Margaret Ritchie said the tourism potential had been largely untapped.
"It fell into serious neglect for many, many years," she said.
"Nobody, including myself, would have been terribly aware of the historical significance of the Mound of Down or even have the ability to get to it.
"The major sleeping giant of the area is tourism. It is our gateway to jobs and a stimulus to the local economy. We must develop that."
"I made representations to my party colleague, the Minister for the Environment Alex Attwood. I invited him out to the Mound of Down, we walked it and saw the commanding views of Down Cathedral, of Inch Abbey and other areas associated with the Patrician legacy.
"This is a place rich in history.
"Downpatrick was long on the map before other seats of government were in place on this island."
Bob Bleakley from the Environment Agency is overseeing the work at the site which will take six weeks.
"By cutting just a couple of wedges in the vegetation, it will expose the mound to views and we've chosen angles that provide views from important sites.
"By opening it up it can become a major tourist attraction, along with other sites on the St Patrick's Trail."