The Hotel de Ville is built on the site of the Roman Forum. The underground passages or Cryptoportiques dating from the 1st century BC are all that is left from the Forum and are accessed from Hotel de Ville. (small charge)
The passageways provided a firm foundation for the forum building and are made up of three U shaped passageways with two small service entrances. They have barrel shaped vaults and a central row of arches giving extra strength and support. They were too damp to be used for storage. Later on they were partitioned off to provide cellars for houses built above them.
This doesn’t feature on the tourist tick list and there isn’t a lot of information in the guide books or on the web.They can possibly be best summed up as rather esoteric, and definitely different! There isn’t a lot to see so this is probably one for the real Roman buffs…