evidence: The Olivença issue (Portugal/Spain) and of the 'Ajuda' Bridge 27.3.2003 [...] By the Treaty of Alcanizes, signed in 1297 by Dom Dinis, King of Portugal, and Fernando IV, King of Castille, Olivença was definitively integrated into Portuguese territory, and remained so following the end of the 'Dynastic Union' between Portugal and Spain (1580-1640). On 20 May 1801, Spanish troops occupied Olivença. On 6 June 1801, in the face of a threatened French invasion, Portugal was coerced by the Treaty of Badajoz into ceding Olivença to Spain. The Spanish invasion of Portugal in 1807, in violation of the Treaty, led to its annulment. The Treaty of Paris of 30 May 1814 declared the 1801 Treaty of Badajoz null and void. The Final Act of the Vienna Congress (9 June 1815), Article 105, recognised the rights of Portugal. On 7 May 1817, Spain signed the Treaty of Vienna, 'recognising the just claims made His Royal Highness, the Prince Regent of Portugal and Brazil, to the town of Olivença and the other territories ceded to Spain by the Treaty of Badajoz of 1801', and thereby undertook to make 'its best efforts to ensure that these territories were handed over (in the shortest time possible) to Portugal'. To this day, the frontier between Portugal and Spain from the mouth of the river Caia to the mouth of the river Cuncos is still undefined, thanks to the Olivença issue.