Just because unicorns are mythical doesn’t mean they haven’t had a real impact on history. Just ask a narwhal! Find out everything you need to know about unicorns as you prepare to celebrate National Unicorn Day on April 9.

1. The first known depiction of a unicorn—found in the Lascaux Caves of modern-day France—dates to around 15,000 BCE! Or so people thought, until they realized that the so-called Lascaux unicorn had two horns, drawn confusingly close together.

2. The earliest record of unicorns in Western literature belongs to Greek historian Ctesias. In the 5th century BCE, he wrote that the beast had a white body, purple head, blue eyes, and a multicolored horn—red at the tip, black in the middle, and white at the base.

3. In his travels, Marco Polo believed he stumbled across unicorns. He wrote, “They are very ugly brutes to look at. They are not at all such as we describe unicorns.” That’s because they were actually rhinoceroses.