The ancient caravan routes took the slaves and products like ivory to the following coastal cities on the East African coast:
Mombassa (see slide-show for photo of Fort Jesus)
Zanzibar island was during the 19th century the steppingstone and depot for this trade. Most caravans were organised, resourced and funded from Zanzibar. Slaves were shipped with dhows to Zanzibar where they were sold on the slave-market. From Zanzibar slaves and ivory were transported to many different places e.g. Muscat and Sur in Oman but also to French colonies. Around 1890 Bagamoyo became the capital of the German DOAG colonial company.
To control the East African trade Western powers took control of the coastal cities over from the Omani Arabs. Initially this was done by the Portuguese in the 16th century. Then during the 17th century the Omani claimed back the cities and later in the 19th century the Germans and British took control. The Portuguese mention that in the 16th century they built the large Fort Jesus close to the Arab city (Mombassa). Later during the 17th century the Omani conquered the large fort and drove the Portuguese away.
Before the Portuguese arrived the coastal cities were probably controlled by the Kingdom of Hormuz that was run by Persians and Omani Arabs. According to Omani tradition it was the Al Harthi tribe that founded Mombassa many centuries ago.