Nida was an ancient Roman town in the area today occupied by the northwestern suburbs of Frankfurt am Main, Germany, specifically Frankfurt-Heddernheim, on the edge of the Wetterau region. At the time of the Roman empire, it was the capital of the Civitas Taunensium. The name of the settlement is known thanks to written sources from Roman times and probably derives from the name of the adjacent river Nidda.

Frankfurt am Main is the most populous city in the German state of Hesse. Its 773,068 inhabitants as of 2022 make it the fifth-most populous city in Germany, and it is the only city in the country rated as an "alpha world city" according to GaWC. Located in the foreland of the Taunus on its namesake Main, it forms a continuous conurbation with the neighbouring city of Offenbach am Main and its urban area has a population of over 2.3 million. The city is the heart of the larger Rhine-Main metropolitan region, which has a population of more than 5.8 million and is Germany's second-largest metropolitan region after the Rhine-Ruhr region and the fourth biggest metropolitan region by GDP in the European Union. Frankfurt is home to the European Central Bank, one of the institutional seats of the European Union, while Frankfurt's central business district lies about 90 km (56 mi) northwest of the geographic center of the EU at Gadheim in Lower Franconia. Like France and Franconia, the city is named after the Franks. Frankfurt is the largest city in the Rhenish Franconian dialect area.