We spent 4-5 hours at Constitution Hill total, but could have spent more time to see the court building, old prison and fortress that make up this site. Each have their own highlights. I was somewhat disappointed that they didn't keep the prison very well maintained, but otherwise it was interesting. Kids would be ok exploring the various rooms and passages, and there is a children's room in the fortress. Another interesting aspect of the history of South Africa specific to Johannesburg for adults. Bring some water, and remember there are only one set of toilets near the staircase towers.
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