Located on the north bank of the Tagus estuary, the growth of Lisbon relied greatly on the river and the sea. It was the river that enabled the first dispersed settlement, on the top of the castle hill, and attracted groups such as the Phoenicians, Greeks and Carthaginians, who came to the city to trade. Others followed, including the Romans and later the Visigoths, until the arrival of the Moors in the 8th century.
During the Roman occupation, the city of "Felicitas Julia Olisipo" (Lisbon) became an important Roman "Municipium" in the 1st century AD under the rule of Julius Caeser, due to its port, garum, wine and horses. It’s also important to note that it was the crossing point of 4 Roman roads, 3 to Mérida (in present-day Spain, this being the capital of the province of Lusitânia) and 1 to Bracara (the present city of Braga).
These groups were the first to build a factory for salting fish, which was caught in the waters of Lisbon and Tróia and later salted with salt from Setúbal and sent to the rest of the Empire in splendid amphorae, a trade that was vital to the area. Salt is today one of the country's natural resources, and its main exported product since the Middle Ages, existing in large quantities at the mouths of the main Portuguese rivers.
At that time, the Tagus had two important tributaries: one flowing into Avenida Almirante Reis and the other towards Avenida da Liberdade, which transformed into a small stream, now non-existent.
The Roman city of Lisbon had a forum, temples, spas, villas, theatres, circus and cryptoporticos, the latter constituting true underground cities, in other words, it consisted of an underground gallery, that is, an underground structure that was used to level the ground and lay the buildings, eliminating the slope of the place where the forum was to be built. In short, it was like a monument, about 5 meters high and 10 meters wide.
Similarly to the previous inhabitants, the Moors established themselves here over the course of 4 centuries, denominating the city "Lixabona" or "Al-Uxbûna". They promoted the urban layout of the Al-hama quarter, developing small, winding streets, narrow lanes and family courtyards situated on the hill. Lixabona prospered due to its gold, silver, fertile land, thermal waters in Alfama, clean air and abundance of fish. The Moorish town had walls and several gates, the main gate having impressive marble columns. It was in this area that the wealthier Moorish population built their noble houses.
The transformation of Lisbon as the centre of the world dates back to the Golden Age of Portuguese discoveries in the 15th and 16th centuries, due to the goods and wealth brought to Europe from the Portuguese colonies in Africa, India and Brazil, such as spices, fabrics, precious stones, among others.
At that time, King Manuel I transferred the Royal Palace from St. George's Castle, to a new palace then built by the Tagus River, called "Ribeira Palace", from where the king could see the arrival of the caravels loaded with all kinds of products, to the port of Lisbon, at "Cais das Colunas”. At this time, many foreigners started living in Lisbon, not only Europeans.
It was certainly during this period that Lisbon changed radically, with the river becoming the most important element of the city's spatial organization. Although in the 17th and 18th centuries Lisbon continued to face the Tagus, the river ceased to be the centre of city life. With the growth in the 19th century of the great avenues, not depending as much on the Tagus.
The Tagus was born in Spain, in the Albarracin Mountain Range, it bathes Toledo in Spain and Abrantes and Santarém already on national territory, covering a distance of 1007 km, 256 km of which in Portuguese territory. It flows into Lisbon, maintaining over the centuries a very strong connection between the two countries, contributing to the evolution of Lisbon society, whether in an urban-spatial sense or in a historical and cultural social sense.