Something silver glitters in the dirt. Should thirteen-year-old Luca Malaschnitschenko pass it by? He almost does. But he takes a second look. The bit resembles garbage—perhaps a useless piece of aluminum. Luca and his teacher clean the object. It isn’t trash. It’s a coin.

The two treasure hunters are amateurs. They use metal detectors to make this big find on the island of Ruegen in the Baltic Sea. Professional archaeologists ask them to keep their discovery a secret for a while. Then the archaeologists take time to plan and dig. They find a whole hoard of treasure! Pearls and brooches? Check. Rings and necklaces? Check. And let’s not forget the 600 chipped coins. More than 100 of them go way back—to the time King Bluetooth ruled.

You read that right: King Bluetooth! Harald Gormsson lived in the 10th century. He was one of the last Viking kings. He ruled what is now Denmark, northern Germany, southern Sweden, and parts of Norway. He was called Bluetooth because he had a dead tooth that looked bluish. People remember King Bluetooth for bringing unity to Denmark. Of course, the word “Bluetooth” means something else to us today. Wireless Bluetooth technology was invented by the Swedish company Ericsson. Bluetooth makes computers work with cellular devices (such as phones) without any wires having to be attached. Company officials named the technology after Harald Bluetooth. Bluetooth tech does just what Harald Bluetooth did. It unites things!

We remember Harald Bluetooth for another reason too. He turned his back on old Norse religion and his people’s made-up gods. He placed an engraved rock in Denmark called the Great Jelling Stone. In runes (ancient Germanic letters), the stone says King Bluetooth “won for himself all of Denmark and Norway and made the Danes Christian.”