It's Wisła.
The Vistula, which is the longest river in Poland
There are many rivers in Poland, however the Vistula is the longest river in Poland.
The longest river, the Nile River, cuts through Egypt.
it is about 651 miles long
The Ruvuma River, is the longest river in Tanzania,
Longest river in Serbia is Danube, it runs 588 km through the country, but their longest river that is within country is probably Morava.
Egypt has the world's longest river, the Nile River.
The longest river is Laughlin.
The Vistula is the longest river in Poland at 651 miles in length.
Poland and Germany
Italy
Please rephrase - the question is unclear.