On the islands of Colonsay and Oransay there are the remains of many buildings on hill tops, called duns. They are green and covered with grass.
The most impressive of these is Dun Aving or Abhing [..], about one mile west of Scalasaig harbour, and on a commanding hill top. It is circular, and measures about 90 feet diameter. But the outer face of the structure is gone. From it an almost unbroken view of the sea can be had all round the island. Many hundred tons of debris lie at the bottom of the rock on which the fort stands. The site, though not one of the highest hills, is well chosen for defence, and would be almost inaccessible except on one side where the entrance to the fort seems to have been.