A henge is a roughly circular enclosure defined by a bank and, typically, an internal ditch, constructed during the Neolithic or early Bronze Age and understood to have served a ceremonial rather than defensive function. What makes the Milltown example quietly arresting is how thoroughly it has been erased, and how much can still be inferred from what little remains.

Ordnance Survey maps tell the story of the monument's gradual disappearance. The 1840 six-inch edition shows a large circular enclosure roughly 50 metres across, still legible on the landscape. By the time the 25-inch edition was produced, it had shrunk somewhat in depiction, measuring around 40 metres north-west to south-east. By the 1921 edition of the six-inch map, it had vanished from the cartographic record entirely, suggesting it was levelled sometime in the intervening decades, probably as agricultural improvement extended across the ridge. When surveyors from the North Munster Project of the Discovery Programme visited in 1997, they identified a very broad, low bank, between 9 and 13 metres wide, giving an overall diameter of approximately 52 metres. A more detailed inspection in 2017 found an oval area roughly 32 metres north to south and 28 metres east to west, defined by a scarp only 25 centimetres high in places, with a more pronounced internal scarp on the western side, where the ground drops into a dish-shaped interior from an area of exposed rock. A possible entrance, about 6 metres wide, appears to survive at the western side.

What gives the site its wider significance is its neighbourhood. Four megalithic tombs lie within a 270-metre radius, positioned to the east, south-east, and north-west, with further comparable monuments scattered across the surrounding area. This clustering suggests that the ridge at Milltown was a focus of prehistoric activity over an extended period, with the henge forming one node in a denser ceremonial landscape than the tidy fields of modern Clare might easily suggest.