The first question every tour guide asks you when you walk around Stone Town is, do you want to go to Prison Island? Changuu Island is called Prison Island because ages ago all those with yellow fever cases were quarantined on the island to separate them from the population of Zanzibar but no prisoners were ever held there. The island is easily accessible by boat from Stonetown then upon entering the facility, visitors are required to pay a small entry fee, and an optional donation when leaving the island. This historical site provides good insight into the history of the prison and what it used to stand for.
The island is now a tourist resort which houses endangered species of giant tortoises that were originally a gift from the British governor of the Seychelles. I found the tour of the actual prison more interesting than where the animals were kept mainly due to the fact that there were so many tourists trying to force feed the tortoises cabbage and take pictures for their social media it became more of a circus, less enjoyable and rather chaotic which I thought took away from the conservation aspect.