We received this product (and most of its accessories) as a birthday gift when our son turned three. After getting the castle set up, he absolutely loved pulling out each new piece, unpacking it, and seeing how it interacted with the castle.
The castle itself is fairly large, but it folds inwards and outwards to take up more or less space as needed. The front door opens and closes, and there is a neat feature that bars the doors and windows with the "eagle's talons" when you place a man on the turret and push down. Each of the buttons has one or more sayings (in a charming Scottish (?) accent) associated with it. My husband and I love the front door that says "Who eeeess it?"
Along one wall, there is a piece that "breaks away" when attacked. This works well with the battering ram (purchased separately).
There are ladders, a cannon, and flags, as well as three men figures to play with.
Again, most of the charm lies in the interactions with the different accessories. When the catapult or battering ram are near by and pressed, the castle recognizes them, and the little Scottish voices react accordingly. However, I think that the castle by itself would provide many hours of enjoyment.
My husband bemoans the fact that there was nothing this cool when he was a little boy. I must concur. I, too, would have loved this as a child.