The three largest rivers in Portugal are the Tagus River, the Douro River and the Guadiana River. All three rivers also flow through Spain. The largest river in Portugal is the Tagus River; it is 645 miles long.
The Tagus River flows into the Atlantic Ocean. It flows though major economic areas in Spain and Portugal, so it has been vital to development of both countries.
Portugal is the westernmost country in Europe. The country is bordered by Spain on the north and the east, and it is bordered by the Atlantic Ocean to the west. The capital and largest city in Portugal is Lisbon, which is near the mouth of the Tagus River.