Persian polymath Muḥammad ibn Mūsā al-Khwārizmī (c. 780-c. 850) had a huge influence on the development of algebra, the Hindu-Arabic numeral system, astronomy and cartography. His Kitāb Ṣūrat al-Arḍ (description of the Earth) was a major reworking of Ptolemy's Geography correcting much of his data for The Mediterranean Sea, Africa and Asia. Here is the earliest known map of the Nile River from that work,
some nice details of the origins and branches of the river,
The only surviving copy of this book is in the Strasbourg University Library in France. The copy is in bad shape and parts are almost illegible. Though latitudes and longitudes of thousands of places appear the world map is missing. Historian Hubert Daunicht reconstructed this map, the only copy I can find is this low resolution version from Wikipedia, showing the Indian Ocean.
For fans of "World Music" a band called Guess What named an album Al-Khawarizmi (with a slight spelling difference). The cover includes an early Islamic world map in the lower corner.previous post on this blog has a partial explanation of some of the elements of this map.