Global trade has been a thing for a long time, with items occasionally showing up in odd places. For instance, blue glass beads from Egypt showing up in Bronze-Age Denmark. Now a small cache of ancient Roman coins has popped up in Japan, the first ever found there.
The coins turned up in Okinawa Prefecture, in the UNESCO World Heritage-listed ruins of Katsuren Castle. The building stood from the 12th century to the mid-15th century, when it fell to the army of Ryukyu after the castle's lord, Amawari, plotted against the king.
Among the haul were 4 copper coins dating back to the Roman Empire in around 300 to 400 AD. They had been excavated along with other artefacts, but only identified when visiting archaeologist Toshio Tsukamoto saw them.
"I'd come to analyse artefacts like Japanese samurai armour that had been found there when I spotted the coins," he told CNN. "I'd been on excavation sites in Egypt and Italy and had seen a lot of Roman coins before, so I recognised them immediately."
X-ray analysis confirmed the find. On one side, they bear the likeness of Roman emperor Constantine the Great, who died in 372; on the other, a spear-bearing soldier. Another coin discovered on the site was Ottoman, dating back to 1687.
How they got there is unknown. It was almost definitely trade, but since there is no direct link between Japan and Rome, the coins had to come via China or Southeast Asia. Katsuren Castle had trade relations with both in the 14th and 15th centuries, but the next step will be trying to retrace the exact route the coins travelled.
If you're in or headed to Japan, you can go see these anomalous artefacts for yourself. They'll be on display at the Uruma City Yonagusuku Historical Museum in central Okinawa until November 25.