These sites were the defended homesteads of early Irish farmers and span a very long period of time, from about the 5th century AD up until the later Medieval period.  They consist of a circular area enclosed by a number of raised earthen banks and deep ditches.

marblehill_ringfort

This is a map from the Irish survey cassini 6″

The ancient Ringfort at Marble Hill had a icehouse built into it at a later time period to store ice in for the main house use.

Souterrains are often found in association with ring forts. These are underground chambers with interconnecting passageways.