Archaeologists are baffled by the strange discovery of ancient Roman coins buried in the ruins of a castle in Okinawa, Japan.
The copper coins, which date back to 400AD, are so rare they were originally thought to be a hoax.
They will be analysed further to try to work out how they arrived in Japan. No other Roman coins have ever been found in Japan.
Katsuren Castle, where they were found, dates to between the 12th and 15th centuries, and is a UNESCO World Heritage site.
The coins bear the image of Emperor Constantine I, who ruled from 306 to 337. The most eastern part of the Roman Empire under his leadership was in present-day Saudi Arabia and Syria.
Each coin is about 1.6cm to 2cm wide.
One of the 1600-year-old coins (Uruma Board of Education)
Also found in the ruins was a coin from 17th century Ottoman Empire, which emerged not long after Constantine's rule and at its height covered a similar area to the Eastern Roman Empire (also known as the Byzantine Empire).