Turkmenistan, is a country in Central Asia bordered by Kazakhstan to the northwest, Uzbekistan to the north, east and northeast, Afghanistan to the southeast, Iran to the south and southwest and the Caspian Sea to the west. Ashgabat is the capital and largest city. It is one of the six independent Turkic states. With a population over 7 million, Turkmenistan is the 35th most-populous country in Asia and has the lowest population of the Central Asian republics while being one of the most sparsely populated nations on the Asian continent. Turkmenistan has long served as a thoroughfare for several empires and cultures. Merv is one of the oldest oasis-cities in Central Asia, and was once among the biggest cities in the world. It was also one of the great cities of the Islamic world and an important stop on the Silk Road. Annexed by the Russian Empire in 1881, Turkmenistan figured prominently in the anti-Bolshevik movement in Central Asia. In 1925, Turkmenistan became a constituent republic of the Soviet Union, the Turkmen Soviet Socialist Republic (Turkmen SSR); it became independent after the dissolution of the Soviet Union in 1991.