What is a hillfort?

What a hillfort is

Historic England's introduction to hillforts dates their building and occupation to about 900 to 100 BC, and its scheduling texts date some large multivallate hillforts into the mid-1st century AD; many were reused later, for example as medieval castles. Historic England classes hillforts by size and number of ramparts: slight univallate and large univallate hillforts usually enclose 1 to 10 hectares, while large multivallate hillforts enclose 5 to 85 hectares within two or more concentric lines of earthworks. Promontory forts have one or more ramparts across the neck of a spur or headland, with steep slopes or cliffs forming the rest of the boundary. The Atlas of Hillforts of Britain and Ireland, published in 2017, records 4,147 hillforts across Britain and Ireland, and their size, defensive strength and evidence of occupation vary greatly.

How hillforts look on LiDAR

Hillforts are among the clearest monuments on a bare-earth terrain model: the ramparts show as continuous banks with ditches outside them, following the contour of the hill, and the model shows them under woodland where aerial photographs cannot. Hillshade gives the most readable overall picture, but a rampart that runs parallel to the direction of the light can disappear, so hillshade from several directions or a local relief model is more reliable. Sky-view factor and negative openness pick out the ditches and the entrance gaps, and positive openness shows the crest lines of the ramparts. A local relief model also shows low features in the interior, such as house platforms and quarry hollows, where they survive.

See LiDAR visualisations explained for what each method shows.

What can look like one

Natural scarps, river terraces and the back-scarps of landslips can look like a single rampart, and later field banks, plantation banks and quarry edges can appear to complete a circuit. Medieval ringworks and later stock enclosures are usually smaller but can look similar.

Protection

Many hillforts are scheduled monuments, protected in England by the Ancient Monuments and Archaeological Areas Act 1979 and in Wales by the Historic Environment (Wales) Act 2023.

Examples on the LiDAR

Where they are

Counties with the most hillforts that have a page here.

More examples