Unicorns were once worshipped as symbols of purity and grace. It wasn't until the age of science and discovery that people realised unicorns did not exist and that the "horn" was in fact a narwhal's tusk.
Yet unicorns continue to fascinate people in myths and works of fiction around the world.
Now the horn is on display at the Hong Kong Museum of Art. A new exhibition there showcases some 170 intriguing objects from the British Museum's collection.
A visit opens up a whole new world of pre-modern beliefs.
In times past, we were more at the mercy of Nature. We gathered wood from forests for shelter, hunted fish from the seas for food, and skinned animals from the savannahs for clothes.
"We were dependent on Mother Earth for survival," notes Rose Lee Wing-chong, the museum's curator of Chinese antiquities. "She had to be appeased, worshipped and feared. This relationship gave Nature a formidable image and fired people's imagination."
People believed the world was populated by magical creatures. They pictured such creatures as having the characteristics of well-known animals in unique combinations.
The Chinese dragon, for instance, combined the long scaly body of a snake, the muzzle of a pig, the horns of a deer, and the teeth and claws of a tiger.
Local farmers worshipped the beast, believing it to be the all-powerful ruler of the skies and waters. They prayed to their "protector" during harvest festivals.
Gradually, this mighty guardian evolved into a royal symbol during the Ming Dynasty. Porcelain vases, golden robes and palaces became emblazoned with dragon images. Neighbouring countries like Japan and Korea, too, worshipped them. In European culture, however, dragons were foes, not guardians. In folktales, they haunted villages and scorched the earth. Heroes and saints battled the powerful beasts.
A 16th century Russian icon on show depicts St George's victory over a dragon in a famous story of medieval literature.
In the story, a dragon terrorises people, eating up women in a town in what is now Libya. God sent St George to kill the beast, which the saint duly did. In gratitude, the villagers converted to Christianity.
Also on display are Egyptian sphinxes. Half-man, half-lion beings, they combine the forces of two worlds into one: pharaohs' intelligence and lions' imposing presence. They guarded tombs, wearing royal dresses.
"From ancient China to Colombia, people created similar hybrid animals to guard the frontier realm between life and death," Lee explains.
Sphinxes, too, became characters in folklore. According to one fable, a female sphinx once terrorised people in the ancient Egyptian city of Thebes.
She devoured anyone who failed to crack her famous riddle: "Which creature walks on four legs in the morning, two legs in the afternoon, and three legs in the evening?" King Oedipus finally worked it out - man (or woman). But her riddle can still perplex people today.
Another eye-catching item in the exhibition is a North American thunderbird. The colourful wooden carving dates from the 19th century and was once used during potlatch festivals when tribes met and exchanged gifts.
"These majestic birds could fly to all corners of the world," Lee says. "The indigenous people of America believed they had the power to relay messages to their gods and spirits."
The exhibition is on show until April 11 at the Museum of Art