Most maps made in twelfth century Europe were based on tradition and myth rather than scientific information. The only practical maps were mariners’ charts that showed coastlines, ports of call, shallows and places to take on provisions and water. Roger II, the Christian king of Sicily, wanted a map of the known world that was a factual as a mariner’s chart. In 1138, he hired well-known Muslim scholar al-Sharif al-Idrisi to collect and evaluate all available geographic knowledge and organize it into an accurate picture of the world.

For 15 years, al-Idrisi and a group of scholars studied and compared the work of previous geographers. They interviewed the crews of ships who docked at Sicily’s busy ports. They sent scientific expeditions, including draftsmen and cartographers, to collect information about relatively unknown places.

Finally, al-Idrisi was ready to make his map. He began by making a working copy on a drawing board, using compasses to accurately site individual places. The final copy was engraved on a great silver disk that was almost eighty inches in diameter and weighed over 300 pounds. Al-Idrisi explained that the disk was just a symbol for the shape of the world: “the earth is round like a sphere, and the waters adhere to it and are maintained on it through natural equilibrium which suffers no variation”

Al-Idrisi’s map was accompanied by a descriptive geography that contained all the information his college of geographers had collected. Its formal name was Nuzhat al-Mushtaq fi Ikhtiraq al-Afaq, or The Delight of One Who Wishes to Traverse the Regions of the World. It was more commonly known as Roger’s Book.

In 1160, the Sicilian barons revolted against Roger’s son, William. They looted the palace and burned the library, including Roger’s Book. Not surprisingly, the silver map disappeared. Al-Idrisi fled to North Africa with the Arabic text of Roger’s Book. His work survived in the Islamic world, but it was not available in Europe again until the Arabic text was printed in Rome in 1592.