Late in the 11th century a band of marauding mercenaries looted the Spanish Arab city of Toledo. What they found there shook Christian Europe to its foundations.In mountain-top monasteries, the flame of learning had been kept alive in a sea of Dark Age ignorance. But this universe was changed forever by the treasure from Toledo that came across the Pyrenees. In Italy it gave us law and university life; in France the towering Gothic cathedrals. And in the dawn light of the north African desert it showed us how to make a rainbow.