The Rhine (German: Rhein; Dutch: Rijn; French: Rhin) is a European river that runs from the Swiss canton of Grisons in the southeastern Swiss Alps through Germany and eventually flows into the North Sea coast in the Netherlands and is the twelfth longest river in Europe, at about 1,233 km (766 mi), with an average discharge of more than 2,000 m3/s (71,000 cu ft/s).
The Rhine and the Danube formed most of the northern inland frontier of the Roman Empire and, since those days, the Rhine has been a vital and navigable waterway carrying trade and goods deep inland. It has also served as a defensive feature and has been the basis for regional and international borders. The many castles and prehistoric fortifications along the Rhine testify to its importance as a waterway. River traffic could be stopped at these locations, usually for the purpose of collecting tolls, by the state that controlled that portion of the river.
Basel (pron.: /ˈbɑːzəl/) or Basle (pron.: /ˈbɑːl/; German: Basel; pronounced [ˈbaːzəl]) is Switzerland's third most populous city with about 166,000 inhabitants. Located where the Swiss, French and German borders meet, Basel also has suburbs in France and Germany. In 2011, the Basel agglomeration was the third largest in Switzerland with a population of 500,600 in 74 municipalities in Switzerland and an additional 53 in neighboring countries (municipal count as of 2000). The tri-national metropolitan area has around 830,000 inhabitants in 226 municipalities.