The viola d'amore shares many features of the viol family. It looks like a thinner treble viol without frets and sometimes with sympathetic strings added. The six-string viola d'amore and the treble viol also have approximately the same ambitus or range of playable notes. Like all viols, it has a flat back. An intricately carved head at the top of the peg box is common on both viols and viola d'amore, although some viols lack one. Unlike the carved heads on viols, the viola d'amore's head occurs most often as Cupid blindfolded to represent the blindness of love. Its sound-holes are commonly in the shape of a flaming sword known as "The Flaming Sword of Islam" (suggesting the instrument's development was influenced by the Islamic World). This was one of the three usual sound hole shapes for viols as well. It is unfretted, and played much like a violin, being held horizontally under the chin. It is about the same size as the modern viola.