7. Portugal and Spain

Border: The line separating Alcoutim, Portugal, and Sanlícar de Guadiana, Spain
Area: 1,214 km (length of the entire boundary)
The estimated GDP is $1.582 trillion for Spain and $276.432 billion for Portugal.
The zipline that whisks adventure seekers from Sanlúcar de Guadiana in Spain to Alcoutim in Portugal is an exciting variation on international travel that can be found near the border between Spain and Portugal. Known as Limitezero, this unusual means of transit represents the cordial relations between these two countries in addition to offering a fresh approach to crossing borders.

Portugal and Spain @insider/Pinterest
Participants glide from one country to the next, experiencing the unique feeling of momentarily hopping across time zones. The course spans the Guadiana River. It is the first cross-border zipline in the world and embodies a spirit of international unity and adventure, making crossing borders an amazing experience.