There's not much to visit inside the castle except the the battlements, prison and tower view. Walking around the battlements leads you to a human-power wheel to raise water, left over from when the castle was a prison. The history museum is well laid out and interesting - particularly the later items - but it does overlap with the other history museums in the town. I went on the guided tour, but apart from hearing the history did not really give access to any of the closed parts of the castle, so wasn't really worth the extra. if you have a Ljubljana Tourist Card, you need to pay again for the guided tour.
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