Luxembourg () (Luxembourgish: Lëtzebuerg ; German: Luxemburg), officially the Grand Duchy of Luxembourg, is a landlocked country in western Europe. It is bordered by Belgium to the west and north, Germany to the east, and France to the south. Its capital, Luxembourg City, is, together with Brussels and Strasbourg, one of the three official capitals of the European Union and the seat of the European Court of Justice, the highest juridical authority in the EU. Its culture, people and languages are highly intertwined with its neighbours, making it essentially a mixture of French and Germanic cultures. This is emphasised by the three official languages, Luxembourgish, French, and German. The repeated invasions by its neighbour countries, especially in World War II, resulted in the country's strong will for mediation between France and Germany and, among other things, led to the foundation of the European Union. With an area of 2,586 square kilometres (998 sq mi), it is one of the smallest sovereign states in Europe, about the same size as the US state of Rhode Island or the English county of Northamptonshire. In 2016, Luxembourg had a population of 576 249, which makes it one of the least-populous countries in Europe, but by far the one with the highest population growth rate. As a representative democracy with a constitutional monarch, it is headed by a Grand Duke, Henri, Grand Duke of Luxembourg, and is the world's only remaining grand duchy. Luxembourg is a developed country, with an advanced economy and one of the world's highest GDP (PPP) per capita. The City of Luxembourg with its old quarters and fortifications was declared a UNESCO World Heritage Site in 1994 due to the exceptional preservation of the vast fortifications and the old city. The history of Luxembourg is considered to begin in 963, when count Siegfried I acquired a rocky promontory and its Roman-era fortifications known as Lucilinburhuc, ′little castle′, and the surrounding area from the Imperial Abbey of St. Maximin in nearby Trier. Siegfried's descendants increased their territory through marriage, war and vassal relations. At the end of the 13th century, the Counts of Luxembourg reigned over a considerable territory. In 1308, Henry VII, Count of Luxembourg became King of the Germans and Holy Roman Emperor. The House of Luxembourg produced four Holy Roman Emperors at the high time of the Middle Ages. In 1354, Charles IV elevated the County to the Duchy of Luxembourg. Since Sigismund had no male heir, the Duchy became part of the Burgundian Circle and then one of the Seventeen Provinces of the Habsburg Netherlands. Over the centuries, the City and Fortress of Luxembourg, of great strategic importance situated between the Kingdom of France and the Habsburg territories, was gradually built up to be one of the most reputed fortifications in Europe. After belonging to both the France of Louis XIV and the Austria of Maria Theresia, Luxembourg became part of the First French Republic and Empire under Napoleon. The present-day state of Luxembourg first emerged at the Congress of Vienna in 1815. The Grand-Duchy, with its powerful fortress, became an independent state under the personal possession of William I of the Netherlands with a Prussian garrison to guard the city against another invasion from France. In 1839, following the turmoil of the Belgian Revolution, the purely French-speaking part of Luxembourg was ceded to Belgium and the Luxembourgish-speaking part became what is the present state of Luxembourg. The steel industry exploiting the Red Lands' rich iron-ore grounds in the beginning of the 20th century drove the country's industrialisation. ArcelorMittal, the world's largest steel producer with headquarters in Luxembourg City, is still a reminder of these times. After the decline of the steel industry in the 1970s, the country focused on establishing itself as a global financial centre and developed into the banking hub it is reputed for. Since the beginning of the 21st century, its governments have focused on developing the country into a knowledge economy, with the founding of the University of Luxembourg and a national space programme, projecting the first involvement in a non-manned lunar expedition by 2020. Luxembourg is a founding member of the European Union, OECD, United Nations, NATO, and Benelux, reflecting its political consensus in favour of economic, political, and military integration. The city of Luxembourg, which is the country's capital and largest city, is the seat of several institutions and agencies of the EU. Luxembourg served on the United Nations Security Council for the years 2013 and 2014, which was a first in the country's history. In 2016 Luxembourgish citizens had visa-free or visa-on-arrival access to 172 countries and territories, ranking the Luxembourgian passport equal 15th in the world, tied with countries such as Canada and Switzerland.