Prison Island Zanzibar, also known locally as Changuu, is best known today for a colony of giant tortoises rather than the prison its name promises.
The name is the first thing to get wrong about this place: Prison Island was built as a prison in 1893, and it never held a single prisoner. What it actually became — a quarantine station, then a leisure retreat, and now home to one of the world’s most dramatic tortoise-conservation comeback stories — is a far better reason to take the twenty-minute boat ride out from Stone Town than the name suggests. Looking for a place to sleep nearby? where to stay in Stone Town breaks down the options.
Prison Island Zanzibar: A Prison That Never Held a Single Prisoner
In 1893, Lloyd Mathews, the British-appointed First Minister of the Zanzibar protectorate, bought the small coral island then known by its Swahili name, Changuu, with plans to build a prison for violent and repeat offenders from the mainland. Construction finished by 1894. Then the plan simply stalled, and the buildings sat empty — “Prison Island” is a nickname that stuck to a prison that was never actually used as one, a detail confirmed by historical research into Zanzibar’s colonial-era archives.
You’ll also come across claims, repeated on plenty of tour listings, that the island was used earlier to hold enslaved people before the 1860s, in the period before Zanzibar’s slave trade was formally abolished. That particular claim is worth treating with some skepticism — more rigorous historical accounts place slave-era detention in a fort on the Stone Town seafront itself, not on this island. Changuu’s own documented history starts with the prison that wasn’t, not with the slave trade.
From Quarantine Station to Leisure Retreat
The empty prison blocks found a real purpose a few years later. A plague outbreak in India in 1898, combined with heavy ship traffic of indentured laborers bound for the Uganda railway, meant East Africa’s colonial authorities needed a regional quarantine station — and Changuu’s unused buildings were repurposed to hold arrivals, mainly for yellow fever observation, for one to two weeks at a time. A larger quarantine complex went up on the island’s southwest side in 1931, and the island was formally renamed “Quarantine Island” in 1923.
That function faded by the mid-20th century as the need for mass quarantine declined, and the island quietly became something closer to a private retreat for Europeans living in Zanzibar — old coral-mining pits were turned into swimming pools, and a bungalow built for visiting dignitaries now operates as a small restaurant. Today it’s neither a prison nor a quarantine station — it’s a short, slightly strange day trip built around one genuinely remarkable animal.
The Tortoises: A Population That Nearly Vanished
The island’s Aldabra giant tortoises — a species native to a single atoll in the Seychelles, more than 2,500 km away — arrived as a gift. In 1919, the British Governor of the Seychelles sent four of them to Zanzibar, and they became the founding population of what’s now one of the most visited tortoise colonies outside their native range.
The numbers tell a rough story. The colony grew to roughly 200 tortoises by 1955, then collapsed under poaching pressure for the pet and meat trade: down to about 100 by 1988, 50 by 1990, and just 7 surviving adults by 1996. A recovery effort that year — backed by what’s now World Animal Protection — introduced 80 hatchlings and built a proper protective enclosure; by 2000 the island held 17 adults, 50 juveniles, and 90 hatchlings. Conservation and breeding work has continued since, and the colony today numbers somewhere around 100 tortoises of mixed ages, though no precise current census is published.
You’ll hear guides claim some of the tortoises are upwards of 190 years old — treat that as a tour-guide talking point rather than a verified fact. No scientific source backs an age anywhere near that for any tortoise on the island; it’s safer to say some of the original 1919 arrivals could plausibly be past 100, which is still a genuinely old animal, without repeating the more dramatic number.
Visiting the Tortoises
A handler is typically on hand at the enclosure to supervise feeding — cabbage and other greens are usually sold or provided right at the entrance rather than something you bring yourself — and to explain the colony’s history while you’re there. Hand-feeding is normally allowed, but guides will tell you to watch the tortoises’ necks, which move faster than their bodies suggest. Children should not be lifted onto a tortoise’s shell for a photo; it’s explicitly discouraged, not a judgment call to make on the spot. Outside the feeding area, the old prison and quarantine buildings are generally open to wander through at your own pace.
Entrance Fees: What Changed in September 2025
Zanzibar revised entrance pricing for its marine conservation areas — a zone covering Changuu and nearby Bawe Island together with Mnemba, Menai Bay, Chumbe, and the Pemba Channel — effective 1 September 2025. The rate for foreign visitors outside East Africa rose from $3 to $10 per adult; non-EAC residents of Tanzania pay around $5; East African Community citizens pay roughly 5,000 TZS (about $2); children under 5 remain free, with children 5–15 generally paying about half the adult foreign rate. That $10 figure is the bare government gate fee — most visitors never pay it on its own, since it’s bundled into a tour package alongside the boat transfer, a guide, and sometimes lunch or snorkel gear, which typically pushes the total to somewhere between $35 and $90 depending on what’s included. If you book through an operator or your hotel, ask specifically whether the conservation fee is already included in the quoted price, since not every listing makes that clear.
Getting There
Boats leave from the Stone Town waterfront, near Forodhani Gardens, for a crossing that takes roughly 20 minutes each way — though it can run closer to 30 minutes and get genuinely choppy if the wind’s up. There’s no scheduled public ferry: independent travelers negotiate a fare directly with boat owners on the beach, which is cheaper but means haggling and no guide once you arrive; a pre-booked tour costs more but removes that step and usually includes a guide at the tortoise enclosure. Most organized trips run on a rough late-morning-pickup, early-afternoon-return schedule, though no official opening hours are published for the island itself — worth a quick check with your operator or hotel rather than assuming a fixed time window.
Snorkeling and the Rest of the Island
The water on the sandy, boat-landing side of the island is generally calm and reasonably clear, though it can feel a little congested with boat traffic during busy mid-morning hours. The opposite side has a harder coral floor and is more tide-dependent, so it’s less suited to a casual swim. A small restaurant in the former European bungalow and a bar in part of the old prison building serve food and drinks, though neither reliably operates outside peak season — bring your own water and snacks rather than counting on buying them there.
Who This Actually Suits
Prison Island suits travelers doing a Stone Town day who want one further, self-contained outing that doesn’t require a full beach-village relocation — families with kids who’ll enjoy the tortoises specifically, and anyone curious about Zanzibar’s quieter colonial history alongside the animals. It’s a half-day add-on, not a destination that needs its own overnight stay. If you’re nearby, Nakupenda Sandbank is worth folding into the same day.
When to Go
June through October and December through February bring calmer seas and a smoother boat crossing. March through May’s long rains make the water rougher and increase the odds of a cancelled or postponed trip.
Good to Know Before You Go
The conservation fee changed in September 2025: budget around $10 per foreign adult for the bare entrance fee, more if it’s bundled into a tour package with transfer and a guide.
Don’t believe the “190-year-old tortoise” claim at face value: it’s a popular guide talking point without a verified source behind it — the tortoises are still genuinely old, just not quite that old.
No riding tortoises, ever: guides and staff actively discourage lifting children onto a tortoise’s shell for photos.
Bring cash, water, and snacks: the island’s restaurant and bar don’t reliably operate outside peak season, and the entrance fee and any independent boat fare are typically cash transactions.
FAQ
Was Prison Island ever actually used as a prison?
No — it was built as one in 1893–94, but the plan was never carried out, and the buildings sat empty before being converted into a quarantine station a few years later.
How much does it cost to visit Prison Island in 2025–2026?
The government marine conservation fee is about $10 for foreign visitors, $5 for foreign residents of Tanzania, and roughly 5,000 TZS (about $2) for East African Community citizens, effective since September 2025. Most visitors pay this as part of a bundled tour price of roughly $35–$90.
Where did the giant tortoises come from?
Four Aldabra giant tortoises were sent as a gift from the British Governor of the Seychelles in 1919. The population crashed to just 7 adults by 1996 due to poaching before a conservation program rebuilt it to around 100 tortoises today.
How do I get to Prison Island?
By boat from the Stone Town waterfront near Forodhani Gardens, roughly a 20-minute crossing each way. There’s no scheduled ferry — you either negotiate a boat directly on the beach or book a tour that includes transfer.
Is Prison Island worth visiting if I only have one day in Stone Town?
It works well as a half-day add-on to a Stone Town day rather than something that needs its own overnight stay — reasonable for travelers who want the tortoises and a bit of offbeat colonial history without committing a full extra day.