The bridge lies on a bronze age highway between the cities of Tiryns and Epidauros. The ruins of both cities still exist, by the way, and are well worth a look.
This is a drystone construction with a tiny arch in the middle. The downward pressure of gravity combined with the solid placement of the rocks holds everything in place. Those rocks have sat there for about 3,300 years. Yes, this thing was built in about 1300BC.
When people first walked across this bridge, Minoan civilization was on its last legs. It was the post-palatial period, when Knossos declined and Mycenae rose. Local villagers use it to this day.