This irregular oval enclosure, stretching 215 metres from west to east-northeast and measuring 114 metres from north to south, was only discovered in 2014 through lidar technology that can peer through vegetation to reveal archaeological features. The monument crowns parts of the summit, enclosing an impressive area of 2.5 hectares within its earthen boundaries.

What makes this hillfort particularly intriguing is how clearly it demonstrates the limitations of traditional archaeological survey methods. The western section shows the most distinct traces, appearing as a series of curved earthworks that extend across the hilltop, whilst the northern and southern boundaries remain more subtle and difficult to detect. Subsequent geophysical surveys in 2018 helped archaeologists better understand the fort’s structure, revealing it as a poorly preserved but substantial Iron Age defensive site.

The hillfort doesn’t stand alone on Windmill Hill. Within its ancient boundaries, you’ll find a collection of monuments spanning different periods: a historic windmill, an ancient cairn, and a ceremonial enclosure with its associated smaller enclosure. Just southeast of the main fort lies a ring-ditch, another archaeological feature that adds to the rich tapestry of human activity on this Dublin hilltop. Together, these monuments tell the story of a landscape that has been significant to people for thousands of years, from prehistoric ceremonies to medieval grain processing.