Vitrified forts are another puzzling one - ancient fortresses where the stones in the walls have been subjected to enough heat to make them melt together - whether this was done on purpose or by accident or by enemy action is unknown:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Vitrified_fort" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Vitrified_fort</a><p>NB As a kid the impressive vitrified fort on the Tap o&#x27; Noth was by basis for imagining what Tolkien&#x27;s Weathertop looked like.