The ruins of an extensive mountain village have been found on the slopes of the Sugar Loaf, near Abergavenny.
Among the ruins were 25 cottages and a road
Scouts working with the British Trust for Conservation Volunteers have spent a week hacking back brambles to reveal the 25-house village.
It is thought the Y Graig settlement in Glangrwyne, Powys, was abandoned in the 19th Century after its landlord increased villagers' rent.
Conservationists believe there may be more buildings to be uncovered.
Keith Stockdale from the British Trust of Conservation Volunteers said: "There are at least 25 houses - a complete village with several hundred people with orchards and hundreds of animals like pigs and goats and donkeys."
Mr Stockdale said the village was likely to have been abandoned because of rising rents.
He said: "The village probably fell into private hands and the landlord decided to put up the rent.
"The villagers didn't have the money so he came and took all their animals to Abergavenny market to pay for it.
"The villagers all left because their livelihoods had gone and the landlord probably came and smashed the doors and roofs so no one would come back.
"And it hasn't been touched since it was abandoned about 150 years ago."
As the undergrowth which had hidden the village for so long was cleared away, the size of the village became clear.
There is a drovers road, cottages, a bakery, toilets and a two-storey building further up the mountainside.
There was also the discovery of a rare beehive pigsty which is almost identical to one that was taken away from another site brick by brick and rebuilt at the Museum of Welsh Life in St Fagans, Cardiff.
An inscription above a doorway has been uncovered which dates to 1746.
The village is thought to have been lived in from the early 1700s to the mid or late 19th century.
Mr Stockdale said the existence of the village was brought to his attention by Cadw, the Welsh historic monuments agency, who had been contacted by someone living locally.
"Someone came up and realised there was an awful lot of history here," he said.
During the clear up which was done by scouts from the Gloucester area, a walkway has been put in place complete with steps to allow people to wander through the whole village.
"I think there is a lot more to be found here - it goes right up the mountainside," he added.
Cadw is supporting the reclamation of the village.
A spokesman said: "This is a complete post-medieval village of great historical and archaeological importance."