The Iron Age
The weather seems to have worsened towards the end of the Bronze Age (about 2,700 years ago), and upland houses and fields became abandoned to the encroaching peat. At the same time we find the first clear evidence of conflict - hillforts with great ramparts to protect people and their animals from attack. Some hillfort ramparts in Highland, especially around the Moray Firth, have been set on fire and burned so fiercely that the stones have fused together. This is known as vitrification and it can be seen at Craig Phadraig, Inverness, or Knockfarrel, Dingwall. It is not known why or how this was done. Recent experiments have failed to establish the answer.
At the same time, iron working was being introduced. This requires much higher temperatures to work than bronze but the result is much harder and more durable. Hut circles continue through the Iron Age, and increasingly we find evidence of field boundary walls as well as groups of clearance heaps.
The Roman Empire never conquered the Highlands but nevertheless there was a sophisticated local culture here which traded with the Romans. Caithness is the heartland of the broch, a uniquely Scottish type of round stone tower with hollow walls dating from about 200 BC to 200 AD. Some of these have been excavated and have produced traded Roman finds. The finest brochs to visit in Highland are in Glenelg (Dun Troddan and Dun Telve). At Rubh an Dunain on Skye, there is a broch-like stone wall defending a rocky headland, and a variety of other types of Iron Age fort, many of them called duns, are found. Often these make use of natural defensive features such as sea-cliffs.
Duns and brochs were not just for defence. They also indicated the status of the chief who lived there. Crannogs for example would have had limited defensive potential in an age of boat transport as they were houses built on artificial islands, in lochs. Many of these local centres of power seem to have continued in use well into the medieval period - there are references to crannogs still being occupied in the 16th century.
Another curious type of site associated with the Iron Age is the souterrain. This is a curved underground tunnel built of stone slabs. There are good examples in Skye, Sutherland, and at Easter Raitts in Badenoch. We do not know what they were built for originally but later they seem to have been used for storage and for hiding from enemies. The entrances to souterrains often seem to lead from the inside of houses.
From the 4th century AD the people of northern Scotland were being referred to by Roman writers as 'Picti' - painted people. These people produced characteristic symbols which are found carved on stone and also on finds of jewellery from the period. Pictish stones are found all over the Highlands, but there is a concentration in the east. Some of the great Pictish carved cross-slabs such as those in Easter Ross are magnificent works of art dating to the 8th - 10th centuries AD, with influences from Northumbria, Ireland, and Scandinavia. These combine Pictish and Christian symbolism.