Some buildings serve a purpose. Kinnoull Tower is not one of them — and that is precisely the point.
Perched on a rocky outcrop near the 222-metre summit of Kinnoull Hill, above the winding River Tay outside Perth, the tower is a folly.  It was never a fortress. Nobody defended it. Nobody lived in it. It was built, quite simply, because one man thought it looked good.
That man was Thomas Hay, the 9th Earl of Kinnoull, who built the tower in the eighteenth century after completing his Grand Tour of Europe. He had been rather taken with the castles lining the Rhine in Germany, and spotted what he considered a pleasing similarity between those dramatic river gorges and the rocky cliffs on his own estate. 
So he did what any self-respecting Georgian aristocrat would do. He built his own version.
The young Jane Austen visited in September 1789, describing it in her early writing as “An old and Mouldering Castle, which is situated two miles from Perth on a bold projecting Rock.”
It has been mouldering rather well ever since.
Today the tower is a Category B listed structure, reached by a winding footpath through the woodland park. A short walk rewards you with one of the finest views in Perthshire — which is, of course, exactly what the Earl had in mind.