One of the better known ancient monuments in the Monasteraden area is Clogher stone fort or cashel (Irish caiseal from Latin castellum). It is located within the Coolavin Demesne a short distance west of Monasteraden Village. This stone fort is well preserved having undergone extensive re-building in the 19th century.
It consists of an area enclosed by a circular stone wall which is 26m in diameter. The wall is constructed with large boulders at the base and progressively smaller slabs towards the top. There are a series of stepped ramps leading to wall walks, which allow access to the ramparts. The walls are 4.3m thick and 2m high. The entrance is a plain 1.8m wide passage and located on the south-east side.
The interior of the stone fort is raised by about one meter, perhaps, to accommodate the souterrains. These are underground structures, normally consisting of one or more passages and chambers. Generally, they are drystone constructions but some are rock-cut. They functioned as places of refuge and storage and are common to many ringforts.
One souterrain is located on the north-east of the entrance leading into the wall. It extends into the wall, turns left and extends through the wall and leads into a short chamber. In the south-west part of the site is a flight of 8 steps, which leads into another souterrain passage. This passage extends to the south for 8.1m and under the wall. It then extends up into a ’creep’, designed to reduce access and put an attacker at a disadvantage. It turns west into a curving passage for a considerable distance.
Stone forts or cashels are the equivalent of earthen banked ring forts but are much less common. Ring forts are Ireland’s most common field monument with 45,000 recorded examples. Dating of ring forts is difficult but most of those that survive are thought to have been built well after the first century with many built or used right into the medieval period (800 – 1500 AD).
Stone forts or cashels belong mainly to the Early Christian Period (450 – 800 AD) but some date from an earlier time.
The introductions of iron weapons and structural changes to society are thought to have led to a great increase in cattle farming leading, in turn, to an increase in cattle raiding and warfare. Cattle were the real unit and source of wealth at this time. Many such sites give excellent views which suggest that they may have been built more for status than for defence.