Karlsruhe (ˈkɑːrlzruːə , USalsoˈkɑːrls- , ˈkaʁlsˌʁuːə; South Franconian: Kallsruh) is the third-largest city of the German state (Land) of Baden-Württemberg after its capital Stuttgart and Mannheim, and the 22nd-largest city in the nation, with 308,436 inhabitants. It is also a former capital of Baden, a historic region named after Hohenbaden Castle in the city of Baden-Baden. Located on the right bank of the Rhine near the French border, between the Mannheim/Ludwigshafen conurbation to the north and Strasbourg/Kehl to the south, Karlsruhe is Germany's legal center, being home to the Federal Constitutional Court (Bundesverfassungsgericht), the Federal Court of Justice (Bundesgerichtshof) and the Public Prosecutor General of the Federal Court of Justice (Generalbundesanwalt beim Bundesgerichtshof).
Karlsruhe was the capital of the Margraviate of Baden-Durlach (Durlach: 1565–1718; Karlsruhe: 1718–1771), the Margraviate of Baden (1771–1803), the Electorate of Baden (1803–1806), the Grand Duchy of Baden (1806–1918), and the Republic of Baden (1918–1945). Its most remarkable building is Karlsruhe Palace, which was built in 1715. There are nine institutions of higher education in the city, most notably the Karlsruhe Institute of Technology (Karlsruher Institut für Technologie). Karlsruhe/Baden-Baden Airport (Flughafen Karlsruhe/Baden-Baden) is the second-busiest airport of Baden-Württemberg after Stuttgart Airport, and the 17th-busiest airport of Germany.
Karlsruhe lies completely to the east of the Rhine, and almost completely on the Upper Rhine Plain. It contains the Turmberg in the east, and also lies on the borders of the Kraichgau leading to the Northern Black Forest.
The Rhine, one of the world's most important shipping routes, forms the western limits of the city, beyond which lie the towns of Maximiliansau and Wörth am Rhein in the German state of Rhineland-Palatinate. The city centre is about from the river, as measured from the Marktplatz (Market Square).