Lisbon lies along the northern banks of the River Tagus (Rio Tejo) and the slow flowing water of the river helped create Lisbon the city that it is today. The protection that the estuary offered from the ferocious Atlantic attracted the early settlers which developed into a major Roman port. Later the Age of Discover, regarded as the golden age of Portugal, originated from the docks of the Rio Tejo and the wealth of the colonies flowed back along the Tagus River to fund the extravagance of the era. The Portuguese as a nation are travellers with communities dotted throughout the world and this characteristic can be traced back to the close connection with the seas and the rivers of which the Tejo is the most important.
The River Tagus flows into the Lisbon region from the north of Portugal and opens into a wide but shallow estuary that boarders Lisbon to the east. The estuary flows out into the Atlantic Ocean in a westerly direction between the high cliff headlands on the south bank and the flatter slopes of the capital.
At the narrowest point of the mouth of the Tagus estuary the Ponte de 25th Abril suspension bridge connects the capital with the southern commuter distracts of Almada. This bottle neck travelling south was alleviated by the Vasco da Gama Bridge which stretches out from eastern Lisbon for 17km to the western bank of the Rio Tejo estuary.
The Tagus River originates from central Spain (the Serra de Albarracín) and cuts a generally westerly course for 716 km (445 miles) until the Portuguese boarder. The Tagus slows significantly close to the boarder and meanders southwards forming the frontier between Spain and Portugal for 47 km (29 miles). The final 275 km (171 miles) is within Portugal where it provides a constant water supply for farm irrigation to an otherwise arid region.
The total length of the Rio Tejo is 1,038 km (645 miles) and is the third longest river of the Iberian Peninsula behind Douro and the Ebro Rivers but the Tejo drains the second largest basin of the peninsula at 80,100 square kilometres (30,927 square miles).