Massive - and abandoned

These massive walls at Froghall stand almost alone in the midst of a forested valley.  One wonders at first if they are the remains of a castle.

However, it's clear that they are built on to the side of a hillside - so castle they are not.

They actually are kilns - the doorways being where the raw material was loaded ready for firing. The raw material in this instance was limestone, quarried nearby, to make lime (for agriculture mostly).

It turns out this abandoned area - now a beauty spot - was a thriving industrial centre in the nineteenth century.   Ozymandias would have appreciated the irony.