Scotland a territorial parish structure, with every community in Scotland having a local congregation. Scotland also has a significant Roman Catholic population, 19% professing that faith, particularly in Greater Glasgow and the north-west. After the Reformation, Roman Catholicism in Scotland continued in the Highlands and some western islands like Uist and Barra, and it was strengthened during the 19th century by immigration from Ireland. Other Christian denominations in Scotland include the Free Church of Scotland, and various other Presbyterian offshoots. Scotland's third largest church is the Scottish Episcopal Church. Islam is the largest non-Christian religion (estimated at around 75,000, which is
Hillforts in Scotland settlement developed in the Hownam model is still seen as having some validity. A. H. A. Hogg identified four types of hillfort: contour forts, promontory forts, cliff forts and ridge forts. Contour forts, where banks and ditches are moulded to the shape of the hill, are the dominant form in Scotland. Less significant are promontory forts, usually employing coastal features, such as the largest one in Scotland at the Mull of Galloway. Different types of defensive style occurred throughout the Iron Age period, some of which may have been a response to Roman siege warfare. There were different combinations in