Peter walks on the Via Domitia, the old Roman Road (built in 118 BC) which led between the Alps and the Pyrenees.
This trace is in the centre of Narbonne and strangely the streets still follow its line.
Most of it is now covered by the Languedocienne, the motorway which covers its course by the Mediterranean.
It is still in amazing nick when you consider the amount of chariots and legions which marched along its length all that time ago- not to mention the damage Hannibal must have done with his ruddy elephants.