Prison Island

Twenty-five minutes by boat from Stone Town’s waterfront, a small island in the Zanzibar Channel holds a colony of giant tortoises who have been here longer than the country that now manages them. The oldest individuals at Prison Island (also known as Changuu Island) are estimated to be over 150 years old — meaning they were alive during the height of the Zanzibar Sultanate, the Abushiri revolt, the Anglo-Zanzibar War and both World Wars, and have outlived every political system that has tried to govern them.

The island is Zanzibar’s most popular half-day excursion from Stone Town, combining the tortoise colony, a historical colonial fort, a reef snorkel and a sandy beach. It takes about 3–4 hours door-to-door.

Where is Prison Island?

In the Zanzibar Channel, 5.6 km northwest of Stone Town. Dhow and motorboat transfers run from the Stone Town waterfront; operators line the harbour near the Tembo Hotel. Trips include the crossing, island entry fee and time at the island; snorkelling equipment is available for rent on the island.

The Aldabra giant tortoises

The colony was established in 1919 when General Lloyd Matthews (British colonial administrator) received four tortoises as a gift from the governor of the Seychelles. The colony has grown through subsequent additions to approximately 100 animals today. The Aldabra giant tortoise is native to Aldabra Atoll in the Outer Seychelles; the Zanzibar population is one of the few outside their home island.

The tortoises roam freely on the island and are extraordinarily tolerant of visitors — they have been handled and photographed for over a century. Feeding them by hand is permitted; the island sells appropriate food. The oldest tortoises have had their ages assessed by wildlife vets and are believed to exceed 150 years, making them among the oldest living animals on Earth.

The historic fort

The island was originally used by the Zanzibar Sultanate as a holding place for rebel slaves awaiting shipment — a grim chapter documented in the Stone Town Slave Museum. The British colonial administration began constructing a formal prison on the island in 1894 (hence the name), but it was completed and then converted to a yellow fever quarantine station before any prisoners ever occupied it. The building still stands and is open to visitors.

Snorkelling

The reef surrounding Prison Island has healthy coral cover and good reef fish diversity — a solid beginner snorkel, though not as spectacular as Mnemba Island. The protected waters are calm and clear in both dry seasons, making it accessible to any swimming ability.

Combine with…

• Stone Town — always the base for the trip.
• Nakupenda Beach — the sandbank day trip can sometimes be combined on the same boat.

Frequently asked questions about Prison Island

How old are the tortoises on Prison Island?

The oldest are estimated at over 150 years; the island has records of tortoises donated in 1919 whose ages at the time were unknown. Some may predate 1900.

Why is it called Prison Island if it was never a prison?

The British began construction of a prison in 1894 which was completed but never used for prisoners — it was converted immediately to a yellow fever quarantine station instead. The name “Prison Island” stuck regardless.