Imagine your teacher shows you a box. Inside, there's a broken cup, a tiny statue of an animal, and a few stones arranged in a circle. "These belong to people who lived 4000 years ago," she says. "Now tell me what they believed in."

When divers found a lump of green, crusty metal on the seabed, who knew that it would turn out to be one of the most amazing inventions of the ancient world!