250 mile optical telegraph in the Byzantine Empire in the 9th century CE

The Byzantine Empire used a system of beacons (an optical telegraph) to transmit messages across Asia Minor to Constantinople. The main line of beacons stretched over some 450 miles (720 km). A message could be transmitted the entire length of the line within an hour. #Seshat pic.twitter.com/QhTJ3ffET9

— Seshat (@SeshatDatabank) August 18, 2018