Archaeological discoveries have been made within yards of the by-pass currently under construction in Nenagh, Co Tipperary.
At Ballintotty on the Dublin road, the remains of a 13th-century hall house have been uncovered.
A neo-lithic site calculated to be 5,000 years old was unearthed at Tullaheady on the Limerick road.
Part of the bottom half of the Ballintotty hall house remains intact. The ground floor measures 12 metres by 10 metres, with stone walls one and a half metres thick.
It would have comprised two small rooms. There is evidence of the remains of a spiral staircase.
It was built for defence purposes and the occupiers would have been loyal to Nenagh Castle.
There are some examples of such houses in other parts of the county, though very few, if any, have been excavated, says archaeologist Mr Pat Logue, who is directing the excavation.
A quantity of medieval pottery was also found, as well as a cooking area, and horseshoes and horseshoe nails.
Discoveries at the Tullaheady site include stone axes, arrowheads and stone beads.
It has been described by Mr Logue as "one of the finest prehistoric sites in Ireland".