A crannog is a type of ancient lough dwelling. Most are circular structures that seem to have been built on artificial islands as individual homes to accommodate extended families.
According to the DRD (Department of Regional Development), which is building the new by-pass: "Roads Service has been aware for some time of the presence of an historic crannog site on the line of the new Cherrymount Link Road in Enniskillen.
"In consultation with NIEA (Northern Ireland Environment Agency), the site is being resolved by a team of archaeologists who are currently on site," it added.
NIEA is responsible for preserving ancient monuments and buildings.
A DRD spokesman explained: "The Medieval site, at least 700 years old, has revealed evidence of its timber-and-soil construction, as well as a wicker-walled structure, possibly a house. It has also produced fragments of mill stones, wooden plates, small crucibles for metal-working, vast quantities of pottery and even pieces of cloth and part of a wooden plough.
"Some human remains were discovered, though it is thought that this was not their original burial place," the spokesman added.
"Two arrowheads found on the site, and dating to 3,000 or 4,000 years ago, were probably brought in accidentally with soil to build up the crannog," he explained.
"The work of the archaeologists is expected to continue over the summer. To date, a number of items of archaeological significance have been found and many will require further verification through laboratory testing, which will be carried out on completion of their site works," he said.
The excavations are not expected to interfere with the completion of the new road. "Work is well advanced on the adjoining new length of carriageway which links this roundabout to the Coa Road," said the spokesman.
"Road widening of the existing Cherrymount Link Road to the north of the scheme is also progressing well and the treatment of lengths of poor ground throughout the scheme has now been substantially completed," he added.
"The new road remains on target for completion and opening to traffic in early 2013," he stated.