About 500 BC, island society moved into the Iron Age. The buildings became larger and more prominent, culminating in the brochs – circular, dry-stone towers belonging to the local chieftains – testifying to the uncertain nature of life then. The best remaining example of a broch in Lewis is at Dùn Chàrlabhaigh. The Scots arrived during the first centuries AD, bringing the Scottish Gaelic language with them. As Christianity began to spread through the islands in the 6th and later centuries, following Columban missionaries, Lewis was inhabited by the Picts.