The river that crosses Seville is a long waterway that traverses Andalusia from East to West, covering a distance of 410 miles. The Romans used to call it “Betis”, which is the reason why the entire region was named “Betica” in Roman times. When the Arabs arrived the river was given its current name: Guadalquivir, which means Great River. It was a most convenient commercial road, yet, at the same time, it posed a great threat for Seville, as it would frequently flood and, most importantly, it exposed the city to the danger of potential invasion from the river. In fact, it was essentially the river that facilitated the Vikings who, in the year 844, invaded and destroyed a sizable part of the Islamic city! They were eventually repelled by the local forces, but new walls and defences were needed.