This is a folly named Kinnaull Tower on Kinnuall Hill outside of Perth on the left hand side of the A90 as you drive towards Dundee.
The path to the folly is found at the back side when viewed from the A90. Access is gained from following the signs to Perth City Centre and turning right before the hotel on the right hand side.
There is a fantastic view of The River Tay and some very nice walks. The climb to the top is easy and well worth the effort. Care must be taken as there are very steep drops down to the A90. More information on this tower can be found here.