Off the pristine coast of Zanzibar, Tanzania, lies one of archaeology's greatest mysteries - the lost trading city of Rhapta. This legendary port, described by ancient Greek and Roman geographers as a bustling hub of East African commerce, has captivated explorers for centuries. Join the underwater adventure where Josh Gates dove into remote waters, exploring shipwrecks and ancient ruins that emerge only during low tide.
Zanzibar is a Tanzanian archipelago in the Indian Ocean off the coast of East Africa, consisting of two main islands — Unguja (the larger island, commonly called Zanzibar) and Pemba Island — along with numerous smaller islands. The capital, Zanzibar City, is located on Unguja and features the UNESCO World Heritage Site of Stone Town at its historic core. Tourism has grown dramatically from 19,000 visitors in 1985 to approximately 917,000 in 2025, making the islands accessible via five ports and Abeid Amani Karume International Airport, which can accommodate up to 1.5 million passengers annually. Gates investigated the surrounding waters as part of his search for Rhapta, the lost ancient trading city described by Greek and Roman geographers whose exact location has eluded archaeologists for centuries.
Ancient Greek and Roman geographers describe Rhapta as a major trading port somewhere on the East African coast
Zanzibar unites with Tanganyika to form the United Republic of Tanzania
Stone Town designated a UNESCO World Heritage Site
Gates investigates underwater sites and coastal ruins in search of the lost city of Rhapta
Ancient Greek and Roman geographers, including Ptolemy in his 2nd-century work Geography, described Rhapta as a significant trading port on the East African coast, likely dealing in ivory, tortoise shell, and other goods destined for the Mediterranean world. The Periplus of the Erythraean Sea, a 1st-century merchant's guide, also mentions Rhapta as the southernmost trading settlement known to Greco-Roman merchants, placing it somewhere along the coast of modern-day Tanzania. Despite these classical references, mainstream archaeology has yet to definitively locate the city, making it one of the great unsolved mysteries of African coastal history.
The challenge in locating Rhapta stems from several factors that archaeologists acknowledge. Coastal erosion and sea level changes over two millennia may have submerged or destroyed evidence of ancient settlements. Additionally, the East African coast features numerous small islands and shifting shorelines that complicate archaeological survey work. The region's limited systematic underwater archaeology, compared to Mediterranean or Caribbean sites, means potentially significant ruins may remain undocumented beneath the waves or buried under centuries of sediment.
Zanzibar's position in the Indian Ocean trade network makes it a compelling candidate region for Rhapta's location. The archipelago lies at the intersection of maritime routes that have connected Africa, Arabia, India, and beyond for millennia. The islands' historic role in the spice trade and their strategic position along monsoon wind patterns demonstrate the area's long-standing importance to maritime commerce. Gates' investigation explored whether underwater formations and low-tide ruins around Zanzibar could represent the lost city, though the episode's findings remained inconclusive.
The search for Rhapta represents a broader effort to understand ancient African coastal civilizations that mainstream archaeology recognizes as sophisticated trading societies. Unlike speculative theories about lost continents, the existence of Rhapta is documented in historical sources — the question is simply where it was located. Gates' approach, consulting archaeological evidence and exploring potential sites through diving surveys, reflects the methodical work required to solve such historical puzzles, even when definitive answers remain elusive.
Zanzibar is sometimes called the 'Spice Islands' due to its production of cloves, nutmeg, cinnamon, coconut, and black pepper.
Tourism to Zanzibar exploded from just 19,000 visitors in 1985 to approximately 917,000 in 2025, representing nearly a 50-fold increase.
The archipelago is home to the endemic Zanzibar red colobus monkey and the extremely rare or possibly extinct Zanzibar leopard.
Zanzibar's marine ecosystems serve as vital nurseries for fish populations throughout the broader Indian Ocean region.
Zanzibar is readily accessible to international tourists via Abeid Amani Karume International Airport and regular ferry services from mainland Tanzania. Stone Town, the UNESCO World Heritage historic center, offers well-preserved Swahili coastal architecture and is generally safe for visitors, though travelers should check current advisories. The waters around Zanzibar are popular for diving and snorkeling, with numerous operators offering excursions, though accessing specific archaeological sites may require special permissions or expert guides.
Dar es Salaam, Tanzania's largest city, located approximately 25-30 miles west across the Zanzibar Channel on the mainland.
The best time to visit Zanzibar is during the dry seasons from June through October and December through February, when rainfall is minimal and visibility for diving is optimal. The long rains from March to May can make underwater exploration more challenging and some coastal areas less accessible.
Stone Town is a UNESCO World Heritage Site; Zanzibar is a semi-autonomous region of Tanzania
Alexandria
Alexandria was another major ancient port city that played a crucial role in Mediterranean-Indian Ocean trade networks connecting to East Africa.
Dwarka
Dwarka represents another lost ancient port city described in historical texts that Gates has investigated through underwater archaeology.
Myanmar Waters
Myanmar Waters featured Gates conducting similar underwater investigations searching for lost maritime trade settlements in the Indian Ocean region.
Best time to visit: Visit during the dry season from June to September when waters are clearest and low tide reveals the most archaeological features.
Travel tip: Plan your diving excursions around the lunar calendar to maximize low tide opportunities for viewing the submerged ruins.
Historical data sourced from Wikipedia