The map of al-Idrisi dates from 1154

The map of al-Idrisi dates from 1154, and is oriented with south at the top. Note how the east coast of Africa in this map also turns east but does not connect with China; rather, it opens into the “All-Encompassing Ocean.” Thus in the Ptolemaic view, circumnavigation of Africa is impossible, while in al-Idrisi’s view it is technically possible, though too daunting to undertake. UPPER: BRITISH LIBRARY / BRIDGEMAN ART LIBRARY; LOWER: BODLEIAN LIBRARY