west of the town of Fderîck. The date when salt was first extracted from the sebkha is unknown. It is usually assumed that exploitation of the Idjil mines began after the mid 11th century as al-Bakri did not mention them. Instead he described a salt mine at a place that he called 'Tatantal'. Historians have usually assumed this corresponds to Tegahza but his description could possibly also apply to the mines at Idjil. According to Pereira, in 1487 the Portuguese built an entrepôt in Ouadane in an attempt to gain access to the trans-Saharan gold, salt and slave trade. The entrepôt was probably short lived and is not mentioned in the detailed description provided by Fernandes. In the 16th century the Moroccans made various attempts to take control of the trans-Saharan trade in salt and especially that in gold from the Sudan. They organised military expeditions to occupy Ouadane in 1543-44 and again in 1584. Then in 1585 they occupied Taghaza and finally in 1591 their victory in the battle of Battle of Tondibi led to the collapse of the Songhay Empire. Tegherbeyat, the upper ruined section of the town, is almost certainly the oldest. It would have originally contained a mosque but nothing has survived. The ruins of the lower section of the town include a mosque that was probably built in the 15th century when the town expanded. Some of the horseshoe arches are still standing and some walls still have the remains of clay plaster, suggesting that the mosque was abandoned sometime in the 19th century. The mosque measured 24 m north–south at its eastern end and 17 m north–south at its western end where the minaret would have stood. From east to west it would have measured 15 m. The terrace was supported by five rows of horseshoe arches. At the eastern end are the remains of an external mirhab and a courtyard measuring 13 by 12 meters that would have been used in hot weather. Gallery See also Museum of Ouadane References Sources . . . Reprinted by Holmes & Meier in 1980. . . . . The Portuguese text is available online from the Internet Archive. . . . . Further reading . . Includes a plan on page 155. . External links OUADANE: The old caravan centre World Heritage Listing 1147 establishments 12th-century establishments in Africa Former Portuguese colonies World Heritage Sites in