On an island of coral rock at the edge of the Indian Ocean, a city was being born. Mombasa, which Kenyan school history books place as founded around 900 AD, grew from a modest Swahili settlement into one of the great port cities of the medieval world. Ships from Arabia, Persia, India and China docked in its harbour. Merchants haggled in a language that was neither fully African nor fully Arabic but something entirely new. The city that rose from that coral island would anchor Kenya's coast for over a thousand years.