Brochs are double skinned, dry stone towers, originally 30 - 40 foot high. They are unique to Scotland and were built over a 300 year period around the time of Christ. The forerunner of the broch is the Atlantic round house, but those are much lower, less ambitious structures. Brochs emerged more or less from nowhere and then were, for some reason, no longer built.
|Dun Telve, Glenelg|
There were about 500 brochs in Scotland, most of them on coasts where stone is readily available. Sadly, many have since been used as convenient quarries. Dun Telve (above) was depleted to build the nearby barracks at Bernera. The only broch still at its original height is Mousa, on a small island in Shetland.
|Mousa Broch, Shetland|
All brochs are round and very slightly concave, like a cooling tower. Apparently, if they were not double-skinned, they would collapse (I wonder how long it took to learn this!). Remember, they are built without mortar.
There's still a lot we don't know about brochs (not least why they were built). To improve our knowledge, the Caithness Broch Project aims to build a broch which will act as a visitor centre. It's an ambitious undertaking. Ian Armit, in his book 'Towers in the North', quotes an architect's estimate that building a broch would take 400 man days of specialist labour and 5,600 man days of unskilled assistance, assuming that the stone has first been gathered. I salute them!
PS. It is generally accepted that the brochs had a timber and thatch roof. Personally I cannot see how this could have been the case. Could iron age man have constructed a timber roof with a diameter of 18.3 metres (Dun Telve) ten metres above the ground? Would he go to all this trouble to live in darkness, the only light coming from a fire and a low door (which was presumably closed for much of the time)?