Strasbourg is the capital and largest city of the Grand Est region of France and is the official seat of the European Parliament. Located at the border with Germany in the historic region of Alsace, it is the capital of the Bas-Rhin department. In 2016, the city proper had 279,284 inhabitants and both the Eurométropole de Strasbourg and the Arrondissement of Strasbourg had 491,409 inhabitants. Strasbourg's metropolitan area had a population of 785,839 in 2015, making it the ninth largest metro area in France and home to 13% of the Grand Est region's inhabitants; the transnational Eurodistrict Strasbourg-Ortenau had a population of 915,000 inhabitants in 2014. Strasbourg is one of the de facto capitals of the European Union, as it is the seat of several European institutions, such as the Council of Europe and the Eurocorps, as well as the European Parliament and the European Ombudsman of the European Union; the city is the seat of the Central Commission for Navigation on the Rhine and the International Institute of Human Rights.
Strasbourg's historic city centre, the Grande Île, was classified a World Heritage Site by UNESCO in 1988, the first time such an honour was placed on an entire city centre. Strasbourg is immersed in Franco-German culture and although violently disputed throughout history, has been a cultural bridge between France and Germany for centuries through the University of Strasbourg the second largest in France, the coexistence of Catholic and Protestant culture, it is home to the largest Islamic place of worship in France, the Strasbourg Grand Mosque. Economically, Strasbourg is an important centre of manufacturing and engineering, as well as a hub of road and river transportation; the port of Strasbourg is the second largest on the Rhine after Germany. Before the 5th century, the city was known as Argantorati, a Celtic Gaulish name Latinized first as Argentorate, as Argentoratum; that Gaulish name is a compound of -rati, the Gaulish word for fortified enclosures, cognate to the Old Irish ráth, arganto-, the Gaulish word for silver, but any precious metal gold, suggesting either a fortified enclosure located by a river gold mining site, or hoarding gold mined in the nearby rivers.
After the 5th century, the city became known by a different name Gallicized as Strasbourg. That name is of Germanic origin and means "Town of roads"; the modern Stras- is cognate to the German Straße and English street, all of which are derived from Latin strata, while -bourg is cognate to the German Burg and English borough, all of which are derived from Proto-Germanic *burgz. Gregory of Tours was the first to mention the name change: in the tenth book of his History of the Franks written shortly after 590 he said that Egidius, Bishop of Reims, accused of plotting against King Childebert II of Austrasia in favor of his uncle King Chilperic I of Neustria, was tried by a synod of Austrasian bishops in Metz in November 590, found guilty and removed from the priesthood taken "ad Argentoratensem urbem, quam nunc Strateburgum vocant", where he was exiled. Strasbourg is situated at the eastern border of France with Germany; this border is formed by the Rhine, which forms the eastern border of the modern city, facing across the river to the German town Kehl.
The historic core of Strasbourg however lies on the Grande Île in the river Ill, which here flows parallel to, 4 kilometres from, the Rhine. The natural courses of the two rivers join some distance downstream of Strasbourg, although several artificial waterways now connect them within the city; the city lies in the Upper Rhine Plain, at between 132 metres and 151 metres above sea level, with the upland areas of the Vosges Mountains some 20 km to the west and the Black Forest 25 km to the east. This section of the Rhine valley is a major axis of north–south travel, with river traffic on the Rhine itself, major roads and railways paralleling it on both banks; the city is some 397 kilometres east of Paris. The mouth of the Rhine lies 450 kilometres to the north, or 650 kilometres as the river flows, whilst the head of navigation in Basel is some 100 kilometres to the south, or 150 kilometres by river. In spite of its position far inland, Strasbourg's climate is classified as oceanic, but a "semicontinental" climate with some degree of maritime influence in relation to the mild patterns of Western and Southern France.
The city has warm sunny summers and cool, overcast winters. Precipitation is elevated from mid-spring to the end of summer, but remains constant throughout the year, totaling 631.4 mm annually. On average, snow falls 30 days per year; the highest temperature recorded was 38.5 °C in August 2003, during the 2003 European heat wave. The lowest temperature eve