Armenia, officially the Republic of Armenia, is a mountainous country in the South Caucasus region of Eurasia. Located in Western Asia, it is bordered by Turkey to the west, Georgia to the north, the de facto independent Nagorno-Karabakh Republic and Azerbaijan to the east, and Iran and the Azerbaijani exclave of Nakhchivan to the south. Armenia is a unitary, multi-party, democratic nation-state with an ancient cultural heritage. The Satrapy of Armenia was established in the 6th century BC, after the fall of Urartu. In the first century BC the Kingdom of Armenia reached its height under Tigranes the Great. Armenia became the first state in the world to adopt Christianity as its official religion, in between late 3rd to early years of the 4th century (the official date is 301 AD), becoming the first Christian nation." An Armenian principality and later a kingdom, known as Cilician Armenia, existed on the coast of the Mediterranean Sea between the 11th and 14th centuries. Between the 16th and early 19th century, the traditional Armenian homeland composed of Eastern Armenia and Western Armenia came under rule of the rivaling Ottoman and Persian Empires, passing between the two over the centuries. By the mid 19th century, Eastern Armenia had been conquered by Russia, while most of the western parts of the traditional Armenian homeland still remained under Ottoman rule. During World War I, the Armenians living in their ancestral lands in the Ottoman Empire were systematically exterminated in the Armenian Genocide. After almost 600 years of statelessness, Armenia achieved Independence in 1918; however, the First Republic of Armenia, surrounded by hostile countries, was Sovietized in 1920. Between 1922 and 1991, Armenia was part of the Soviet Union. The modern Republic of Armenia became independent in 1991.