The typical mandate of Historic Scotland is to preserve historic places in the state they were found, but the Great Hall of Stirling Castle required some drastic measures. Should it reflect the military period from 1800–1964 or the medieval and renaissance periods? Strategically, the castle has been important for hundreds of years. Castle Hill in Stirling overlooked bogs on one side, and the bridge over the River Forth on the other, so it was the place that controlled trade for the whole region, so the cultural significance of the period from 1600–1800 outweighed the significance of the military period.

But choosing to restore the castle to a state several hundred years in the past is not that simple. First of all, the records aren’t all consistent. The restoration team had a series of etchings of the Great Hall spanning from about 1600 to the late 1800s, and they show the building from various angles. Unfortunately, they all show slightly different things—different numbers and heights of chimneys, for instance. Traditionally the hall had ridge beasts, heraldic statues of unicorns and lions that sit on the apex of the roof. All of the etchings show these, but in varying numbers. So the etchings give an idea of what the castle might have looked like, but as a tool for restoration, they weren’t conclusive.

Source: Scotland’s Stirling Castle: The Great Hall illustrates the complexity of historical restoration, from 99% Invisible.