It is also one of the lowest human density areas in the Iberian Peninsula.

[4][5] For part of its course, the River Tagus forms the boundary between Spain and Portugal.

Areas on both sides of the river are designated as natural parks by the respective nations.

However, while the Portuguese side of the park is a IUCN category V (protected landscape), the Spanish side is categorized as a wilderness area, thus being much more restricted.

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