I visited some Roman ruins approximately 20 km northeast of Paris France. Very nicely excavated - and dated back to approx. 100AD. The archaeologists had found a coliseum, a guard house, a bath house, and a temple.
One of the most interesting aspects of the Wall is Vindolanda, a restored Roman fort with lots of displays and information about life on the edge of the Empire, and how the Roman, Nordic and Celtic cultures met there. As someone of Italian, Swedish and Welsh descent, the place stirred me in ways no other historic site has before or since.
Trier in Western Germany is pretty neat. Among other things, the Porta Nigra is there.