Broch Architecture

In archaeology, a broch is an Iron Age drystone hollow-walled structure found in Scotland, classified by archaeologists since the 1980s as a complex Atlantic roundhouse. The term comes from the Lowland Scots word brough, meaning fort; nineteenth-century antiquaries called the structures burgs, after the identical-meaning Old Norse borg. Roughly five hundred and seventy one candidate broch sites have been identified across Scotland by the Royal Commission on the Ancient and Historical Monuments of Scotland, concentrated in the north of the country, especially Caithness, Sutherland and the Northern Isles, with scattered examples further south including the Scottish Borders. A broch's single entrance was fitted with bar-holes, door-checks and lintels, and its hollow double wall contained mural cells and scarcements, or ledges, with a spiral staircase winding upward between the inner and outer wall to connect galleries at different levels. Internal diameters range from five to fifteen meters, inside walls roughly three meters thick, and while most surviving brochs are partial ruins, five retain walls higher than six and a half meters, including the Broch of Mousa in Shetland, which still stands thirteen meters tall. The first brochs may have been built around 300 BC, though most were raised in the first centuries BC and AD, with construction ending by roughly AD 100 to 200.