regions extend on either side of the Ural River, placing a population of less than one million residents (out of a 15 million total population) geographically in Europe. Because the city of Atyrau straddles the Ural River, it can be considered a transcontinental city. : Russia, the largest country in the world, spans most of northern Eurasia; stretching over a vast expanse of Eastern Europe and Northern Asia. Its sparsely populated Asian territory was historically incorporated into the Tsardom of Russia in the 17th century by conquests. Russia is considered a European country, as it has historical, cultural, ethnical, and political ties to the continent. The vast majority of its population (80%) lives within its European portion, making it the most populous European nation. Russia's capital Moscow is the largest city entirely in Europe. : Turkey falls almost wholly within Western Asia (the Asian portion of Turkey composing the Anatolian Peninsula and additional land) plus a smaller portion of the country in the Balkan Peninsula in Southeastern Europe called East Thrace, which covers only 3% of the country's total area, with a population of about 11 million people, or some 14% of the country's population. Turkey's largest city Istanbul spans both sides of the Bosphorus, making it a "transcontinental city" in both Europe and Asia, while the country's capital Ankara is located in Asia. The territory of the current Turkish state is the core territory of the previous Ottoman Empire that was also transcontinental in the same geographic region, which itself had also supplanted the earlier, similarly transcontinental Byzantine Empire. North America and South America The conventional boundary between North America and South America is at some point on the Colombia–Panama border, with the most common demarcation in atlases and other sources following the Darién Mountains watershed where the Isthmus of Panama meets the South American continent (see Darién Gap). This area encompasses a large watershed, forest and mountains in the northern portion of Colombia's Chocó Department and Panama's Darién Province. Since both Panama and Colombia traditionally view the Americas as a single continent, the Darién border is locally presented not as between the continents of North and South America but rather as between the subcontinental regions of Central and South America. : Since the political boundary between Panama and Colombia is not entirely determined by natural features, some geographers prefer to use the Panama Canal as the physical boundary