Castle lies some twenty miles South of Shepton Mallet - still in Somerset, but only just. A few miles further, and you're in Dorset. It stands proud of the landscape - a wooded, flat oblong of a hill, set in a curve of a long, low ridge. Only from certain angles can you tell that the flat top is bare of trees.
On a later visit to Cadbury, I realised I had misremembered - the top of the hill isn't quite flat - more whale-backed, but with a flat rim.From certain angles, you can discern details in the overall shape which are too regular to belong to an ordinary hill.
It isn't a castle - not in the sense of walls and turrets and drawbridge - even though it served the same purpose in its time. It's a modified hill. To appreciate something of its purpose, you need to get on top.
Not the easiest thing to do - Cadbury Castle is one of the tourist industry's best kept secrets. You could drive round the hill several times before you notice the discreet little entrance, leading up a switchback of ditches and banks to a grassy platform.
Since I was last there, someone has opened a dinky little car park opposite the hill. It's still not all that easy to find.
It is relatively flat on top, and surprisingly spacious; there's plenty of room for buildings, parade grounds, marshalling areas and the like. There's a superb view over the valley to the North and North-East, and over the Somerset plain to the West and North-West. To the South lies a broad slope, rising towards a scarp.
Walking around the edge of the plateau, you can see the regular details which were partly obscured by trees when we looked from below. The sides of the hill are deeply terraced - with broad, deep platforms secure behind stout ramparts. It feels very safe up here; even today, anyone attacking this stronghold would be shagged out by the time they reached the top, and a relatively small defending force could pick off such attackers long before they offered any serious threat.
But such physical properties aren't all that rare; what gives Cadbury Castle its association with Camelot?