Cadzow Castle castle occupies the top of high bluff which rises nearly vertically above the west bank of the Avon Water. Today the castle stands in Chatelheraut Country Park south of Hamilton. It can be reached by paths that lead from the main hunting lodge at Chatelherault and across the Duke's Bridge over the Avon Water.
It helps to know that there are a couple of points in that opening paragraph that need to be qualified. The first is the word "stands". The second is the phrase "can be reached". For some years the castle has been the subject of extensive consolidation work intended to bring a halt to its progressive collapse into the Avon Water far below, and the local advice last time we visited was that this is unlikely to be completed any time soon.
In the meantime Cadzow Castle is largely covered by scaffolding, planks and plastic sheets. And access to the castle itself is prevented by a permanent-looking fence obviously intended to protect both the castle itself from the impact of visitors, and visitors from the impact of a sudden descent into the gorge of the Avon Water after stepping on a loose stone.
One result of all this is that trying to work out exactly what you are looking at as you peer through the fence is not easy. The story of the castle is equally obscure. A Cadzow Castle is known to have existed as far back as 1139 when it served as a hunting lodge for King David I. But it wasn't this Cadzow Castle: instead the early Cadzow Castle seems to have been built next to the River Avon in a location about half a mile north, now covered by the edge of Hamilton. This fell into disrepair and was abandoned in favour of Hamilton Castle, on the site of what later became Hamilton Palace.
Opinions differ, but it is quite possible that when what we today call Cadzow Castle was built by Sir James Hamilton of Finnart in about 1540 it occupied a previously undeveloped site. What was built was designed to withstand an artillery attack and comprised a strongly built keep with drum towers at the south west and south east corners. It has been likened to Craignethan Castle, seven miles to the south east, but neither the written descriptions nor the scaffolding covered bumps on view through the fence make the likeness at all clear.
At the time it was built, the castle was known as The Castle in the Woods of Hamilton. It had a short life. It was visited by Mary Queen of Scots in 1568, but two years later was successfully besieged by the Earl of Lennox. It was again captured, this time by James Douglas, 4th Earl of Morton, in 1579. In the aftermath the castle was slighted to prevent it being used again. Fast forward to 1734, and the architect William Adam completed a grand hunting lodge for the Hamiltons. This was known as Chatelherault and stood on the opposite side of the deep gorge of the Avon Water from the ruins of The Castle in the Woods of Hamilton. In the early 1800s the castle ruins were extensively reworked to turn them into a romantic ruin to be viewed across the gorge from Chatelherault. It may be around the same time that the castle first became known as Cadzow Castle. This was probably to associate the romantic ruins with the spurious heritage from the much older - but completely different - castle of that name.
All this may help explain why Cadzow Castle seems to have been overlooked in the remarkably comprehensive bible of Scottish Castles, The Castellated and Domestic Architecture of Scotland, published by David MacGibbon and Thomas Ross in five volumes between 1887 and 1892. Perhaps they thought it was simply a garden folly.