The De Herefords likely built the impressive motte that still dominates the southern end of Clane village, strategically positioned to control an important River Liffey crossing point just 160 metres to the east. This conical earthwork stands about 8 metres high with a base diameter of roughly 47 metres east to west and 41 metres north to south, tapering to a flat summit approximately 14 metres across. The steep sides, now overgrown with mature trees and briars, conceal a carefully engineered structure; disturbance in the 1970s revealed layers of gravel, small boulders and brown earth, whilst exposed sections at the northern base show alternating bands of clay and fist-sized angular stones.

Local tradition holds that the top of the monument collapsed around 1830, revealing skeletons within, though this remains unverified. In 1940, historian Harold Leask documented a concentric bank and ditch surrounding the motte, though today only a shallow fosse, measuring 3.3 metres wide and 0.7 metres deep, remains visible along the western, northern and south-southeastern edges. A holy well sits just 3 metres to the west, suggesting the site’s continued importance beyond its military function.

Archaeological excavations in 2003 uncovered evidence of medieval activity immediately south of the motte, including two pits containing medieval pottery sherds and animal bones. The larger pit, waterlogged and roughly rectangular at 3 metres long by 2.5 metres wide, yielded 35 pottery sherds alongside charcoal deposits, whilst a smaller circular pit contained five pottery sherds. These finds, along with truncated ditch fragments, paint a picture of sustained occupation around this imposing Norman fortification. The monument has been protected under a preservation order since 1940, ensuring this remarkable piece of Anglo-Norman heritage remains for future generations to explore.