A prison built in 1893 that never held a single prisoner. A quarantine station that guarded the gates of East Africa against yellow fever. Today: giant tortoises older than the 20th century, moving slowly beneath coral stone arches by the Indian Ocean.
Prison Island is one of the most fascinating short excursions in the whole of East Africa — a small coral island whose complicated history of slavery, colonial medicine, and species conservation has produced one of the region's most memorable wildlife encounters.
Officially named Changuu Island — a name almost nobody uses — the island lies just 5 kilometres off the waterfront of Stone Town, accessible by a 20–30 minute ride in a traditional wooden boat. It measures less than one kilometre in length, but the layers of history compressed into that small space are extraordinary.
The island's story begins in the 1860s, when Majid bin Said — the first Sultan of Zanzibar — gave it to Arab slave traders, who used it to hold rebellious enslaved people before selling them at Stone Town's slave market. In 1893, Lloyd Mathews, the British First Minister of Zanzibar, purchased the island and built a prison complex intended for violent criminals from the mainland. The prison was completed in 1894 — but not a single prisoner was ever held there.
Instead, with yellow fever and cholera spreading through East Africa's port cities, the British authorities converted the completed buildings into a quarantine station — the primary quarantine facility for all of British East Africa. Ships arriving in Zanzibar from infected regions would stop here first; passengers suspected of illness were isolated in what had been designed as prison cells, now functioning as hospital rooms. The station operated until the mid-twentieth century, when disease control shifted to other mechanisms. Today, the coral stone buildings — wide verandas, wooden shutters, long corridors — still stand, serving as both museum and shelter for the island's most famous current residents.
In 1919, the British Governor of the Seychelles gifted four Aldabra giant tortoises to the island from the Aldabra Atoll — the species' only natural home on Earth. The tortoises bred, and by 1955 their numbers had reached around 200. By 1996, through theft for the exotic pet trade and bushmeat, only seven remained. Emergency conservation measures — including a dedicated sanctuary and 80 additional hatchlings from the Seychelles — have restored the colony to a thriving, sustainable population. Today these ancient creatures, some over 150 years old and weighing up to 200 kilograms, are Prison Island's defining attraction.
Prison Island's layered history reflects the wider story of Zanzibar's colonial transformation — from the slave trade through British rule, epidemic disease control, and finally conservation. Each era left physical marks on the island that visitors can still trace today.
The island's defining encounter — walking among Aldabra giant tortoises weighing up to 200 kilograms, some of whom were already alive during the First World War. Their ages are painted in blue on their shells by sanctuary staff. Visitors can feed them bundles of fresh spinach (provided by keepers for a small charge); the tortoises move slowly but determinedly toward food, and will gently push against you with their shells. Young tortoises are kept in a separate protective compound. The oldest individuals are estimated at 150–190 years of age — making them some of the longest-lived land animals on Earth.
All Ages · 2-hr Minimum · Sanctuary Entry FeeThe prison complex — completed in 1894 and never used as intended — remains standing in remarkable condition. Long coral stone corridors, wooden-shuttered cells, wide ocean-facing verandas, and the architecturally distinctive European Bungalow (now a restaurant named after Lloyd Mathews) can all be explored. Informational displays explain the island's transformation from slave holding ground to quarantine station to conservation refuge. Some of the tortoises use the prison's shaded corridors as a favoured resting spot — the cells now sheltering the island's most protected residents.
Self-Guided · Included in Entry · 30–60 minPrison Island's western beach offers clear, calm water for swimming — the shallow lagoon is well-protected and suitable for all ages. Snorkelling around the fringing coral reef reveals tropical fish and coral life, though experienced snorkellers will find better reef quality at Mnemba Atoll or Chumbe Island. Many boat captains are happy to combine Prison Island with a visit to the pristine Nakupenda sandbank — a short distance away — for a full day on the water including a seafood barbecue. Swimming at Prison Island is best in the morning before boat traffic increases.
Swim · Snorkel · Combine with NakupendaPrison Island's island grounds are home to a free-roaming colony of peacocks — a striking contrast to the giant tortoises they share the grounds with. The peacocks were introduced as decorative birds in the resort era and have established a semi-wild population that wanders freely between the sanctuary, the old prison buildings, and the beach. Their bright plumage and unexpected presence in this colonial-historic setting creates one of Zanzibar's more surreal wildlife encounters. Birders will also find a variety of seabirds and migratory species along the island's shoreline year-round.
Free-Roaming · No Extra Charge · Year-RoundThe Aldabra giant tortoise (Aldabrachelys gigantea) is one of the world's largest land tortoises and among the longest-lived land animals on Earth. The species is native exclusively to the Aldabra Atoll in the Seychelles — the only location in the Indian Ocean where a large wild population survives naturally. All other populations, including those on Prison Island, exist as a result of deliberate relocation and conservation intervention.
The tortoises at Changuu Island have their estimated ages painted in blue on their shells by sanctuary keepers. The oldest individuals on the island are estimated to be between 150 and 190 years old — born between approximately 1835 and 1875. Some sanctuary staff believe the very oldest animal may be approaching 200 years, which would make it one of the oldest land animals currently confirmed alive on Earth. The celebrated tortoise Jonathan on the island of St Helena (believed born in 1832) is thought to be the oldest known, but the Changuu elders are not far behind.
Adult Aldabra tortoises are entirely herbivorous, feeding on grasses, leaves, and fruit. On Prison Island, keepers supplement natural foraging with fresh spinach and greens, which visitors can feed directly to the animals. The tortoises are calm and accustomed to human presence, but the sanctuary follows strict rules: do not attempt to ride or climb on the tortoises (this is stressful to the animals and strictly prohibited), feed only with keepers' approved greens, and do not use flash photography at close range.
Giant tortoises older than the 20th century, a colonial prison that never held prisoners, and a 20-minute boat ride from Stone Town. Let Haven Trails arrange your Zanzibar excursions.
