With around , inhabitants, it is Germany's 24th-largest city. Wiesbaden forms a conurbation with a population of around , with the neighbouring city of Mainz. This conurbation is in turn embedded in the Rhine-Main Metropolitan Region —Germany's second-largest metropolitan region after Rhine-Ruhr —which also includes the nearby cities of Frankfurt am Main , Darmstadt , Offenbach am Main , and Hanau , and has a combined population exceeding 5.
The city is located on the Rhine Upper Rhine , at the foothills of the Taunus , opposite the Rhineland-Palatine capital of Mainz , and the city centre is located in the wide valley of the small Salzbach stream.
Wiesbaden lies in the Rheingau wine-growing region , one of Germany's 13 wine regions. Historically, Wiesbaden was a Nassauian city. From to , it lay in the County of Nassau , and from to , it was in the county and later principality of Nassau-Idstein, all of which were territories within the Holy Roman Empire ruled by branches of the House of Nassau.
In , the city found itself in the principality of Nassau-Usingen , and in , Biebrich Palace became the main residence of the House of Nassau-Usingen.
In , the city became the capital of the Duchy of Nassau. Since , the newly built Wiesbaden City Palace was the principal Nassauian residence. From to , the city lay in the Prussian Province of Hesse-Nassau , and from to , it was the capital of the Province of Nassau. In , it became the capital of Greater Hesse and subsequently, in , of Hesse.
