What is the largest and most populous city that stands on the river Rhine?

Cologne is the largest city of Germany's most populous federal state of North Rhine-Westphalia and the fourth most populous city in Germany after Berlin, Hamburg, and Munich. Cologne's population is slightly over a million inhabitants. (1.08 million)

It is located on the left bank of the Rhine and is about 45 kilometres (28 mi) southeast of North Rhine-Westphalia's capital of Düsseldorf, and 25 kilometres (16 mi) northwest of Bonn. Düsseldorf, Bonn and Basel are all smaller cities and less populated than Cologne.

Cologne is a 2,000-year-old city and is the region’s cultural hub. It is a city of High Gothic architecture along side a reconstructed old town. The Catholic cathedral is the seat of the Archbishop of Cologne and of the administration of the Archdiocese of Cologne. It is a renowned monument of German Catholicism and Gothic architecture and was declared a World Heritage Site in 1996. It is Germany's most visited landmark, attracting an average of 20,000 people a day, and currently the tallest twin-spired church at 157 m (515 ft) tall.

The adjacent Museum Ludwig showcases 20th-century art, including many masterpieces by Picasso, and the Romano-Germanic Museum houses Roman antiquities.