Unicorn. The unicorn is a legendary creature that has been described since antiquity as a beast with a single large, pointed, spiraling horn projecting from its forehead. The unicorn was depicted in ancient seals of the Indus Valley Civilization and was mentioned by the ancient Greeks in accounts of natural history by various writers, including Ctesias, Strabo, Pliny the Younger, Aelian and Cosmas Indicopleustes. The Bible also describes an animal, the re'em, which some versions translate as unicorn. In European folklore, the unicorn is often depicted as a white horse-like or goat-like animal with a long horn and cloven hooves. In the Middle Ages and Renaissance, it was commonly described as an extremely wild woodland creature, a symbol of purity and grace, which could be captured only by a virgin. In the encyclopedias, its horn was said to have the power to render poisoned water potable and to heal sickness. In medieval and Renaissance times, the tusk of the narwhal was sometimes sold as unicorn horn. The unicorn continues to hold a place in popular culture. It is often used as a symbol of fantasy or rarity. A number of seals seemingly depicting unicorns have been found from the Indus Valley Civilisation. Seals with such a design are thought to be a mark of high social rank. These have also been interpreted as representations of aurochs, a type of large wild cattle that formerly inhabited Europe, Asia and North Africa, or derivatives of aurochs, because the animal is always shown in profile, indicating there may have supposed to have been another horn, which is not seen. Unicorns are not found in Greek mythology, but rather in the accounts of natural history, for Greek writers of natural history were convinced of the reality of unicorns, which they believed lived in India, a distant and fabulous realm for them. The earliest description is from Ctesias, who in his book Indika described them as wild asses, fleet of foot, having a horn a cubit and a half in length, and colored white, red and black. Ctesias got his information while living in Persia. Unicorns on a relief sculpture have been found at the ancient Persian capital of Persepolis in Iran. Aristotle must be following Ctesias when he mentions two one-horned animals, the oryx and the so-called Indian ass. Strabo says that in the Caucasus there were one-horned horses with stag-like heads. Pliny the Elder mentions the oryx and an Indian ox as one-horned beasts, as well as a very fierce animal called the monoceros which has the head of the stag, the feet of the elephant, and the tail of the boar, while the rest of the body is like that of the horse; it makes a deep lowing noise, and has a single black horn, which projects from the middle of its forehead, two cubits in length. In On the Nature of Animals, Aelian, quoting Ctesias, adds that India produces also a one-horned horse, and says that the monoceros was sometimes called cartazonos, which may be a form of the Arabic karkadann, meaning rhinoceros. Cosmas Indicopleustes, a merchant of Alexandria who lived in the 6th century, made a voyage to India and subsequently wrote works on cosmography. He gives a description of a unicorn based on four brass figures in the palace of the King of Ethiopia. He states, from report, that it is impossible to take this ferocious beast alive; and that all its strength lies in its horn. When it finds itself pursued and in danger of capture, it throws itself from a precipice, and turns so aptly in falling, that it receives all the shock upon the horn, and so escapes safe and sound. Medieval knowledge of the fabulous beast stemmed from biblical and ancient sources, and the creature was variously represented as a kind of wild ass, goat, or horse. The predecessor of the medieval bestiary, compiled in Late Antiquity and known as Physiologus, popularized an elaborate allegory in which a unicorn, trapped by a maiden, stood for the Incarnation. As soon as the unicorn sees her, it lays its head on her lap and falls asleep. This became a basic emblematic tag that underlies medieval notions of the unicorn, justifying its appearance in every form of religious art. Interpretations of the unicorn myth focus on the medieval lore of beguiled lovers, whereas some religious writers interpret the unicorn and its death as the Passion of Christ. The myths refer to a beast with one horn that can only be tamed by a virgin; subsequently, some writers translated this into an allegory for Christ's relationship with the Virgin Mary.