Three border areas constitute our field survey :
The Nouvelle-Aquitaine Euskadi Navarre Euroregion (Franco-Spanish border area): GECT which originate from a bilateral cooperation between Aquitaine and Euskadi since 1989,  was established as the Aquitaine-Euskadi Euroregion in 2011. It was consolidated in 2016 with the integration of Navarre and the new departments of the wider Nouvelle-Aquitaine region. Composed by three regions in two different countries, New Aquitaine in France then Euskadi and Navarre in Spain, it has a population of 8,744,648 inhabitants in the 101,678 km² of the territory (https: // www. euroregion-naen.eu/)

Strasbourg-Ortenau Eurodistrict (Franco-German border areas): group created from an Eurodistrict born in 2003 between Strasbourg-Ortenau, it was set up as an GECT in 2007 and expanded in 2015 with three federation of municipalities from the country Erstein, Rhine and Benfeld and surroundings. It currently brings 112 municipalities together – including the 61 French municipalities of the Eurometropolis of Strasbourg and the federation of municipalities of the Canton of Erstein and the 51 German municipalities of Ortenaukreis – where some 958,421 inhabitants live, spread over an area of 2,468 km². (http://www.eurodistrict.eu/)

• Espace Mont-Blanc (Franco-Italian and Franco-Swiss border areas): a space for cross-border collaboration that emerges from awareness in 1986 during the bicentenary of the first ascent of Mont-Blanc, it was created in 1991 with national authorities and regional and local authorities in France, Italy and Switzerland. In 2014, the three Vice-Presidents of the Espace Mont-Blanc signed in Chamonix a declaration of intent for the creation of an GETC, which is currently underway. Espace Mont-Blanc covers territories belonging to the departments of Savoie and Haute-Savoie (France), the Autonomous Region of Aosta Valley (Italy) and the Canton of Valais (Switzerland). In this vast territory, of approximately 3,500 km2, 35 municipalities include this area for 100,000 inhabitants (http://www.espace-mont-blanc.com/).

The choice of these three cross-border areas is justified by their current legal status or in the process of being set up as an EGTC, a fundamental territorial cooperation structure of the European Union adopted by Regulation (EC) No 1082/2006 of the European Parliament and the council relating to the European Grouping of Territorial Cooperation (EGTC). The composition of the areas in question – Euroregion, Eurodistrict and natural area – provides a comparison particularly interesting.