Dover Castle, Kent

English Heritage.
There are diverse things to see on this site: the great medieval castle built by Henry II, the recent re-creation of a medieval castle interior, the church, the Roman lighthouse tower, the Medieval tunnels under the castle, the Napoleonic tunnels in the cliff, and the associated WWII tunnels housing an underground hospital etc, not to mention the cliff-top Admiralty Look-out.
The castle, for once, is a building rather than a ruin, and the recreation of the medieval interior furnishings is interesting. The bright primary colours somehow remind me of a child’s poster paint box. The audio-visual projections using actors are also great fun. The Roman lighthouse tower beside the church looks weather-worn, but it’s amazing that it’s still standing. There is plenty of interest in the cliff-side tunnels which are full of WWII exhibits. There are also great views of the Channel and Dover Harbour.
The Castle could be an all-day visit, but there are some other military relics in the area, such as the Western Heights.