The ‘uncertain’ monuments mean that the sites were not fully understood. In most cases, they have archaeological potential where buried archaeological artifacts are likely to survive. A Scottish broch is a kind of uncertain monument that is an Iron Age drystone hollow-walled structural type built from 800 BC to 250 AD and is found only in Scotland. However, owing to the vast complexity of the building structure and the long unevidenced history, the conservation of brochs has encountered much difficulty, as the archaeology of brochs can be very controversial.