Once a year, during the European Week of Regions and Cities (OPEN DAYS), the CoR welcomes to its headquarters thousands of participants who take part in lively discussions or seek partners to collaborate on joint projects.
Under den årlige afholdelse af Den Europæiske Uge for Regioner og Byer (OPEN DAYS) får Regionsudvalgets hovedsæde besøg af tusindvis af deltagere, der medvirker i livlige debatter eller søger partnere at gennemføre fælles projekter med. 1992: Maastrichttraktaten.