Prison Island - known initially as Changuu Island - was uninhabited until the mid-1860s when Majid bin Salid, the first sultan of Zanzibar, sold it to Arab slave traders. At that time, Zanzibar was at the centre of slave trading in East Africa - the capital, Stone Town, was host to one of the world’s last open slave markets. The traders used Changuu Island as a holding space for slaves in transit to and from Stone Town. Visit Zanzibar's capital today and you'll see museums and monuments to remember this traumatic legacy, including a sculpture of slaves sunken into one of the former cellars of the market.

However by 1873, Sultan Seyyid Barghash signed a treaty that made slavery illegal in Zanzibar - he had done so under great pressure from the British, who had abolished slavery in the UK in 1807. But Zanzibar’s other two main exports - cloves and ivory - allowed the island to flourish commercially. With such abundance, the island began to interest the British, and in 1890 it became a British protectorate. This meant that while it still ruled itself, Britain exercised control over its defence and foreign affairs.

In 1891, The British Consul C. S. Smith visited Stone Town’s prison and was appalled at the squalid conditions and the ‘hot, heavy, foul air’ which made him gag. He suggested that a new prison should be built on Changuu Island. Acting on his recommendation, the British bought the island. They nicknamed it ‘Prison Island’, but progress building the new penal colony was slow. In the interim, European visitors were using the bungalows built for prison staff as a sanatorium, attracted by the sea breezes and pristine environment.

But Prison Island never lived up to its name. By the time it was built, the British were worried about the plagues of cholera, yellow fever and bubonic plague that were ravaging the region. The British authorities, despite the Zanzibar government’s protests, designated Prison Island as East Africa’s main quarantine station. The prison held visitors travelling to Zanzibar for one to two weeks, and also had a medical centre for those exhibiting symptoms of yellow fever.
By the mid-twentieth century, the island was no longer needed as a quarantine station. By then, it had become a popular relaxation spot. Stone Town’s inhabitants relished its quiet beaches after the hubbub of the city; something that continues even to this day. These days there's a resort on the island, complete with ocean-facing swimming pool and sun loungers. You can grab beer and pizza from the former prison restaurant, and eat it on the benches outside the former prison.