evidence: Olivenza (or Olivença) is a small town in Extremadura that’s part of a border dispute between Spain and Portugal. The town is in Spain, but Portugal says it’s rightfully theirs. [...] Although the Guadiana River presents a natural border separating Spain and Portugal, Olivenza, which is another 14 km inland, was part of Portugal from 1297 until 1801. [...] According to Spain, the Treaty of Badajoz has never been revoked and so Olivenza is in Spain. According to Portugal, the treaty was automatically revoked when Spain invaded Portugal in the Peninsular War of 1807 as this broke the terms of the Treaty of Badajoz. Portugal also makes the case that Article 105 of the Treaty of Vienna of 1815 says that Spain must return Olivenza to Portugal