Ballymoon Castle is deemed a National Monument by the Irish Heritage Council and is situated 2miles (3km) east of Mhuine Beag (Bagenalstown), in County Carlow.
This places it some 15 kilometres south of Carlow Town, the county town.
Ballymoon is located in a field adjacent to the Fennagh Road (L33).
It is accessed by a small bridge over a deep field ditch.
Grid ref: S738615.
The castle is thought to date from the 13th century.
The castle has no recorded history, but on architectural grounds it may have been built around 1290-1310 although this subject to some dispute amongst experts.
The most likely builders were the Carew family, who by this time had acquired the area from the Bigods, Earls of Norfolk, or it may have been built by Roger Bigod himself.
It dates to the early 14th century when it was a fortress and was occupied by the Knights Templar although others dispute this, and consider it has been wrongly associated with the Knights Templar.
While some historians suggest that the castle was never completed, most records indicate it was built by Roger Bigod about the year 1300, although as stated arguments abound as they only do in Ireland about both the history and associations of the building.
The castle comprises a courtyard about 80feet (24.
4m) square, with granite walls, 8feet (2.
4m) thick and 20feet (6.
1m) high.
Oblong latrine turrets project from three of its faces; the fourth curtain wall on the western side has no such defense, though the gateway on this side, a plain arch with portcullis grooves, may have had a barbican in front.
The interior is now bare, but the walls feature many embrasures, loops, fireplaces and doors.
