First documented by Carrigan in 1905, this impressive earthwork consists of a raised rectangular platform measuring approximately 70 metres north to south and 52 metres east to west. The site’s defensive architecture reveals the engineering capabilities of its medieval builders, who created a sophisticated system of banks and ditches to protect those within.

The fortification’s design follows a classic pattern of concentric defences. An inner bank, roughly 6.2 metres wide and standing up to 1.5 metres high on its outer face, forms the primary barrier. This is followed by a fosse, or defensive ditch, measuring about 2.7 metres across. Beyond this lies an outer bank, slightly narrower at 4.4 metres wide and reaching 0.9 metres in height on its inner side, with an external fosse approximately 4.6 metres wide completing the southern defences. These measurements, recorded during archaeological surveys, give us a clear picture of the substantial effort required to construct such fortifications.

Moated sites like Rathsaran were typically built during the Anglo-Norman period in Ireland, serving as defended farmsteads for colonists or as administrative centres for local lordships. The raised platform would have supported timber buildings, possibly including a hall, living quarters, and storage structures. Today, while the wooden structures have long since disappeared, the earthworks remain as testament to medieval life in the Irish midlands, offering visitors a chance to walk the same defensive circuits that once protected a thriving medieval community.