A bridge which may date from the medieval period should be refurbished, preserved and secured from further damage, historians and archaeologists have said.
Ardara Bridge at Cadamstown, Co Offaly, at the foot of the Slieve Bloom mountains, has been deemed archaeologically important, especially because it is made of dry stone, with no mortar or lime.
Massive stones are locked together to form an arch, said Mr Paddy Heany, a local historian and author of At the Foot of Slieve Bloom, a history and folklore account of Cadamstown.
Dr Elizabeth FitzPatrick of NUI Galway's archaeology department said the bridge, spanning the Silver River, was a "beautiful structure, a wonderful curiosity in Cadamstown, which deserves to be preserved."
She said there were indications that the bridge dated from the 15th or 16th century, but it might have been an ornamental feature of the later Cadamstown House. This house, dating from the early to mid-19th century, is located about 100 yards from the bridge.
The Archaeological Inventory of Co Offaly says the "impressive stone and mortar bridge . . . is likely to have been associated with nearby Ballymacadam Castle - the medieval stronghold of the O'Carrolls of Leitir Lugna."
There has been no architectural survey of the bridge yet, and radio-carbon dating of mortar, in addition to comparative analysis with other structures from the same period, will be needed to establish its date more accurately, said Dr FitzPatrick.
The bridge is privately owned. It is understood that so far there is no agreement on how the restoration work will proceed.
A spokeswoman for Duchas said it could work on the bridge only if it was in State care. Negotiations, still in their initial stages, were being undertaken and the bridge would, hopefully, be in State care next year.
Owners of the land on either side of the bridge, Ms Catherine Carroll and Mr and Ms Hoare, said they have no objection to the restoration work being carried out.
A spokesman for Offaly County Council said Duchas was acquiring land to enable it to get at the bridge. This acquisition is being funded by the county council.
The bridge, which Mr Heany says is a popular tourist attraction, is 30 feet high and 12 feet wide.
An article on the archaeology of Co Offaly in the magazine Archaeology Ireland in 1994 said: "Unfortunately, this bridge is now in a poor state of preservation and may fall down in the near future if not restored."
Already stone is falling off the north side of the bridge. Over the past three years floods have damaged it, undercutting the foundations and wearing the rock away, said Mr Heany.
"The floods this winter have done a lot of damage. Hopefully next summer, the stone can be reinforced to prevent it from falling. It's going to be a disaster if it falls into the river."