Deep underground in a rock-salt mine in Austria, archaeologists have made an “outstanding” discovery: the 2,200-year-old shoe of a child.

The mine’s rock salt, which people have been mining since the Iron Age (800 B.C. to 1 B.C.) in the village of Dürrnberg near present-day Salzburg, preserved the well-crafted shoe, according to a translated statement from the German Mining Museum (DBM) in Bochum. The lone footwear is about a U.S. children’s size 12 (European children’s size 30).