Centro Region, Portugal known as the Princes of Beira. Along the region’s mountainous border with Spain are a series of fortresses and castles that once protected the country from its many invaders. Over the centuries, Moors, Christians, Spaniards and Portuguese have all tried to take these villages, but their higher elevations usually gave them a distinct advantage. On that border, the more than one dozen fortified frontier villages beckon today’s visitors to come explore a 900-year history — full of the heroism, epic battles and romance upon which Portugal struggled to become a nation. Today, Portugal boasts the longest-standing border in all of
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