A small island off Stone Town with a never-used Victorian prison, a quarantine station and a colony of Aldabra giant tortoises
Changuu is a sliver of coral and trees around 800 metres long, a short boat ride from the Stone Town waterfront. Its popular name, Prison Island, comes from the jail built here in the 1890s, although it never housed a single prisoner. Most visitors come on a half-day trip to see the giant tortoises that roam a protected enclosure at the island's centre, some of them very old and very large.
The crossing itself is part of the appeal: wooden boats putter out across turquoise water, often stopping to snorkel on the reef or at a sandbank on the way. On the island you can walk among the tortoises, look into the old prison cells and relax on the small beach before heading back to town.
Changuu was uninhabited until the 1860s, when Sultan Majid bin Said gave it to two Arab traders who used it to hold rebellious enslaved people before they were shipped abroad or sold in Stone Town. In 1893 Lloyd Mathews, the British first minister of Zanzibar, bought the island for the government and had a prison built for violent and repeat offenders. It was completed in 1894 but never used as a jail.
Instead the island became a quarantine station for British East Africa, mainly for yellow fever, and was officially renamed Quarantine Island in 1923; the old prison served as its hospital. In 1919 the British governor of the Seychelles sent four Aldabra giant tortoises as a gift. The colony grew to around 200 by 1955 but theft for the pet trade and for food reduced it to just a handful by the 1990s. With help from the World Society for the Protection of Animals, the Zanzibar government built a protective enclosure, and new hatchlings were brought in to rebuild the population.
Changuu is government-owned and has no village. Its day-to-day life revolves around the boat crews and guides who bring visitors over from Stone Town, the keepers who look after the tortoises, and the staff of the island's restaurant and hotel.
Trips leave from the beach and waterfront near Stone Town's Forodhani area, usually in the morning or afternoon, and take a few hours including the crossing, time with the tortoises and a swim. Inside the enclosure keepers explain how the animals are cared for, and visitors can usually feed them leaves; the tortoises move slowly and seem unbothered by people, but should not be sat on or lifted.
After the sanctuary, there is time to look at the old prison, walk through the trees and swim or snorkel from the beach. Many boat trips combine Changuu with a stop on a nearby sandbank, which appears only at lower tides.
Trips run year-round, but the sea is calmest and the light clearest in the drier months, from June to October and from December to February. During the long rains between March and May, crossings can be choppy and showers frequent. Go in the morning for calmer water and smaller groups.
Checked against the sources on 28 October 2026. Opening times and fees can change — confirm before you go.
General guidance from our specialists, not official information.
Stone Town is only a short crossing away, and its waterfront, Forodhani Gardens and Old Fort fill the rest of the day. Other islands and sandbanks in the channel can be added to a boat trip. Jozani Chwaka Bay National Park, with its red colobus monkeys, is about an hour's drive from town.
Tanzania · 10 nights5★ LodgeTanzania · 8 nights5★ LodgeTanzania · 5 nights5★ LodgeThis guide was researched from the sources below and reviewed by our team on 28 October 2026. Facts under “Verified information” link to the page they were checked on; travel tips are general guidance. Photos are credited on each image. The ambient recording’s author and licence are shown in the sound player.
