Corona satellite imagery of the wall. Declassified spy photography has uncovered a lost Roman Eastern frontier, dating from the second century AD. Research by archaeologists at the Universities of Glasgow and Exeter has identified a long wall that ran 60 kilometers from the Danube to the Black Sea over what is modern Romania. It is considered the most easterly example of a man-made frontier barrier system in the Roman Empire. Built in the mid-second century AD, 'Trajan's Rampart' as it is known locally, once stood 8.5m wide and over 3.5m high and included at least 32 forts and 31 smaller fortlets along its course. It is thought to have served a similar purpose to other Roman frontier walls, such as Hadrian's Wall, built to defend the Empire from threats to the borders. Trajan's Rampart actually consists of three separate walls of different dates; the 'Small Earthen Wall', the 'Large Earthen Wall' and the 'Stone Wall'. The constructions were previously known about, although wrongly thought to date to the Byzantine or Early medieval period.