Zanzibar was one of the largest slave ports in the vast Indian Ocean slave trade, which was dominated by Arab slave traders. The Arab slave trade originated before Islam and lasted more than a millennium. The slavers hacked their way from Bagamoyo on the Tanzania mainland coast into the African interior, as far west as the Congo.

The slavers traded, bribed chiefs, pillaged and frequently kidnapped to meet the high demand for slaves. The newly acquired slaves were often forced to carry ivory and other goods back to Bagamoyo. The name Bagamoyo is derived from the Kiswahili words "bwaga moyo" which mean 'lay down your heart', because it was here that slaves would abandon any remaining hope of freedom or escape.

Slaves who survived the long and perilous hike from the interior were then crammed into wooden boats called dhows bound for the slave markets in Stone Town, Zanzibar.

Although best known today as an island paradise, there are many prominent reminders of Zanzibar's dark history in the slave trade around Stone Town and across the island. The market where slaves were confined in dark, airless, underground chambers before being sold still contains the chains bolted to the concrete. A moving memorial now stands where the market once was, reminding visitors and locals alike, of the atrocities committed on that very spot centuries before. Nearby, the Anglican Church contains a wooden cross carved from the tree under which the famous explorer and abolitionist David Livingstone's heart was buried in Zambia.