Iron age Britain was dominated by one form of man made structure, that being the Roman road. Arguably the two Roman walls: the Antonine wall and Hadrian’s wall looked more impressive to the naked eye and the garrisons that became towns like Lindum and Veronis held large groups of humanity. The Roman roads did more to change and open up ancient Britain to Roman domination than any other structure. Most of these roads were built between 43 and 410 AD.
Even to this day some of the Roman roads are still in use in great Britain. Although upgraded and mostly covered by bitumen they are still there and are perfectly serviceable millennia later.