Last fall, a Swedish man spotted something in a marsh on Oland, Sweden’s second-largest island. At first, he thought the circular object—found lying on the ground near a construction pit—might be a ...

“From the ornamentation, we were able to date it to the Swedish Viking Age, somewhere between 800 and 1050 C.E.,” Karl-Oskar Erlandsson, an archaeologist at the Kalmar County Administrative ...