Portugal–Spain border Portugal–Spain border The Portugal–Spain border is the international boundary between Portugal and Spain. Referred to as "la Raya" in Spanish and "A Raia" in Portuguese (the stripe), the current demarcation is almost identical to that defined in 1297 by the Treaty of Alcañices. It is one of the oldest borders in the world. The Portugal–Spain border is 1,214 km (754 miles) long and considered the longest uninterrupted border within the European Union. The border is not defined for 18 km (11 miles) between the Caia river and Ribeira de Cuncos, because of the disputed status of Olivenza, which has been
Mongolia–Russia border Mongolia–Russia border The Mongolia–Russia border (, "Mongol-Orosın xil"; , "Rossijsko-mongoljskaja granica") is the international border between the Russian Federation (CIS member) and Mongolia. It is virtually all land. The total length of the border is 3485 km. The boundary is the third longest border between Russia and another country, behind the Kazakhstan-Russia border and the China-Russia border. The Russian state expanded into the regions north of today's Mongolia in the 17th century. Much of the line of the today's Mongolia–Russia border line was set by the Treaty of Kyakhta (1727) between the Russian and Qing Empires (the Mongolia at the