Exceptionally low water levels on the Danube have exposed parts of the foundations of the ancient Constantine Bridge, giving Bulgarian archaeologists a rare opportunity to document what they describe as one of the Roman Empire’s most impressive engineering achievements.

A summer of unprecedented heatwaves has led to record-low water levels in the Danube River.

Exceptionally low water levels on the Danube have exposed parts of the foundations of the ancient Constantine Bridge, giving Bulgarian archaeologists a rare opportunity to…