The slave trade in East Africa was conducted under conditions of utmost brutality by Arab merchants. Slave trade in what is today Kenya was largely curtailed by the presence of Maasai. These were perceived to be fierce warriors, a perception greatly amplified by the Kamba who wanted to keep out competitors in their trade in ivory. Yet the Arabs started to make caravan journeys into the interior by mid 1850s. They followed four principal routes. The first track would originate in Mombasa to Mariakani, Kibwezi, Nzaui, Kitui and then curve westwards into Machakos. The modern road linking Nairobi to Mombasa follows that track with very few diversions. A second route was from Takaungu, a small port near Kilifi, into a place called Silala Magogoni, to Ganze then to either Mariakani or Kibwezi. From these the caravan would strike a northwise march into the highlands. The third route would start from Malindi towards Taveta. From there it would curve northwest to the Rift Valley to move west to the shores of Lake Victoria. An alternative route was from Taveta towards the Ngong Hills and then towards the central highlands. This route had many secondary branches reaching Lake Naivasha and Lake Baringo. After the British imposed a ban on transportation of slaves to Zanzibar in 1873, traders established a fourth route. This followed the coastline from Kilwa, Dar es Salaam, Shimoni, Mombasa, to Lamu. Lamu was an important port in the slave trade even before the Arabs took over from the Portuguese.
Slaves were boarded on dhows at various small ports. Vanga Kuu, on the south coast, was one of these ports. Not far from Vanga is a small village known as Shimoni. The word Shimoni in Swahili means ‘place of the hole’. It was named so because of the presence of a series of caves near the seashore. The caves were used to confine slaves while awaiting shipment to the market in Zanzibar. Old rusted pieces of iron hooks attached to the cave walls are still visible. Malindi, on the north coast, was a rich town. Local plantations and workshops offered much food and commodities for exchange. Slave routes reached Malindi either to board them towards the slave markets in Zanzibar and Muscat, or to trade with the local Swahili population. Western visitors testified that there were public auctions of slaves every Friday in the market located near the two pillar tombs. The slave market was closed in 1885. Slaves were also employed in the plantations between Gede and Malindi. Popular belief says that Jumba la Mtwana, a group of ruins twenty kilometres north of Mombasa, was a slave market. The name Jumba la Mtwana would mean “the hall of slaves”. While it is possible that slaves were kept and traded there, the site seems more a gathering place for Muslim travelling towards the Arabian Peninsula to visit the holy places. From the Kenyan coast, most salves were ferried to the market of Zanzibar for onward shipment to Arabia, Persia, India and even to the Caribbean.