It is where it starts.
river trent
There are 2 cities "Frankfurt" in Germany. There is "Frankfurt am Main" or "Frankfurt / Main". Here is "Main" the river where the city is situated on. This is the Frankfurt with the large airport. The other Frankfurt is situated on the river "Oder". It's in the east of Germany at the border to Poland. This is called "Frankfurt an der Oder" or "Frankfort/Oder".
Polluted river
It means that city lies on the river Main.
The city of N'Djamena is near to Chari or Shari River.
This city is situated on the river 'Main'
There is no river in Vatican City but the Tiber River is quite close.
The Yarra River runs through the city of Melbourne.
It is the main river on which the city of Dublin in Ireland is built.
The main river in the UK is the River Thames. It is the longest river entirely within England, and it flows through the capital and most populated city in the UK, London.
it combines the Oconee and ocmulgee river.