The Schengen zone acts as one country in terms of borders and border controls. As long as you stay in this zone, you can generally cross borders without going through passport control checkpoints again. Similarly, by having a Schengen visa, you do not need to apply for visas to each of the Schengen member
Countries of the Schengen Zone include Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, and Switzerland. Thus when walking the Via Francigena, you enter the zone at Calais.
The Vatican City, surrounded by the city of Rome, doesn’t have formal border controls. However, you do have to go through a metal detector when entering the Vatican Museums or St Peter’s Square, and entry to other parts of the Vatican requires arrangements in advance.
The Schengen Zone covers immigration controls, whilst the EU is effectively a customs union. Therefore, you do not need to pass through customs when travelling between a Schengen and a non-Schengen EU country (eg France to Switzerland). The converse is true for travel between EU and non-EU Schengen countries: you must pass through customs if you have goods to declare, but not immigration.
The CPR receives many questions regarding the time limits for staying within the Schengen Area. We have put together the following document as guidance for pilgrims on the Via Francigena:
Travel in the Schengen zone for non-EU travellers