France‘s longest border is nowhere near Europe, in fact it is nestled within the Amazon Rainforest.

Stretching 450 miles, it is ever longer than France’s border with Spain, which measures 387 miles.

The boundary demarcates the territories of Brazil and France – 5,000 miles from each other. It lies between the Brazilian state of Amapa and French Guiana.

The Oyapock River forms part of this border and is crossed by the Oyapock River Bridge which connects the towns of Saint-Georges in French Guiana and Oiapoque in Brazil.

The origin of this border can be traced back to the Peace Treaty of Utrecht signed between France and Portugal in 1713.

The treaty set the boundaries between the colonial holdings of both kingdoms in South America.

However, due to uncertainty about the location of the Japoc River specified in the treaty as the border, disagreements between France and Brazil (as the successor of the Portuguese Empire) carried on into subsequent centuries.

While France believed the Japoc River mentioned in the treaty to be the Araguari River, Brazil considered it to be the Oiapoque River. The disagreement, known as the Amapa Question, lasted for two centuries.

During this time, France and Brazil established military posts and religious missions, leading to French troops invading Brazilian territory up to the Araguari river, occupying approximately 100,000 square miles of Brazilian land.

In 1900, the territorial dispute was settled in favour of Brazil through international arbitration in Switzerland.

The court examined documents and texts gathered by France and Portugal at the time, concluding that those collected by the Portuguese lent more weight to the Brazilian claim of the border being set at the Oiapoque River.

They also considered the history of the territory and its inhabitants. Apart from minor coastal French settlements, this region of South America was entirely populated by Brazilians and indigenous peoples who identified themselves as Brazilian nationals.