The influence of Islam and the deepening networks of trade spur the growth of several great savanna states, including the Ghana, Mali, and Songhai empires. Further development of metallurgy contributes to both material wealth and artistic production, and Arab reports depict the Ghana empire as the “Land of Gold.” As well as stimulating trade, Islam sparks great cultural and artistic innovation, producing newly syncretic mixes of distinctive regional and Islamic traditions. In 1324–25, the ruler Mansa Musa brings the wealth of the Mali empire to the attention of Europe, North Africa, and Arabia when he completes a pilgrimage to Mecca. Architectural traditions are transformed during the Mali empire. The construction of enormous adobe mosques such as those at Jenne and Timbuktu dates to the thirteenth century. The mosques standing today in West Africa are the product of long histories of construction and reconstruction. They nevertheless reflect the economic conditions, cultural histories, and architectural traditions of the medieval empires from which they originated.