Mombasa travels to the Swahili Coast and made some mention of the city, although he only stayed one night. He noted that the people of Mombasa were Shãfi'i Muslims, religious people, trustworthy and righteous. Their mosques are made of wood, expertly built. The exact founding date of the city is unknown, but it has a long history. Kenyan school history books place the founding of Mombasa as 900 A.D. It must have been already a prosperous trading town in the 12th century, as the Arab geographer Al Idrisi mentions it in 1151. The oldest stone mosque in Mombasa, Mnara, was built
1428 Mombasa years prior to its official discovery at Johannesburg. American astronomer Robert Stephens obtained a rotational lightcurve of "Mombasa" in June 2012. Light-curve analysis gave a rotation period of 16.67 hours with a brightness variation of 0.16 magnitude (). Previous lightcurves were obtained by French amateur astronomer René Roy in February 2006 (17.6 hours, Δ0.15 mag; ), as well as by Scot Hawkins and Richard Ditteon at Oakley Observatory in May 2007 (17.12 hours, Δ0.25 mag; ). On the SMASS taxonomic scheme, "Mombasa" is a , an intermediate between the carbonaceous C and X-type, while it is also described as a