The city was connected by a broad road to Western Hispania's two other large cities, Bracara Augusta in the province of Tarraconensis (Portuguese Braga), and Emerita Augusta, the capital of Lusitania (Mérida, Spain).The city was ruled by an oligarchical council dominated by two families, the Julii and the Cassiae, although regional authority was administered by the Roman Governor of Emerita or directly by Emperor Tiberius.The Indo-European Celts invaded in the 1st millennium BC, mixing with the Pre-Indo-European population, thus giving rise to Celtic-speaking local tribes such as the Cempsi.
Local authorities were granted self-rule over a territory that extended 50 kilometres (31 miles); exempt from taxes, its citizens were given the privileges of Roman citizenship, and it was then integrated with the Roman province of Lusitania (whose capital was Emerita Augusta).
Lusitanian raids and rebellions during Roman occupation required the construction of a wall around the settlement.
Unlike most capital cities, Lisbon's status as the capital of Portugal has never been granted or confirmed officially – by statute or in written form.
Its position as the capital has formed through constitutional convention, making its position as de facto capital a part of the Constitution of Portugal. It has one of the warmest winters of any metropolis in Europe, with average temperatures 15 °C (59 °F) during the day and 8 °C (46 °F) at night from December to February.
During Augustus' reign, the Romans also built a great theatre; the Cassian Baths (underneath Rua da Prata); temples to Jupiter, Diana, Cybele, Tethys and Idea Phrygiae (an uncommon cult from Asia Minor), in addition to temples to the Emperor; a large necropolis under Praça da Figueira; a large forum and other buildings such as insulae (multi-storied apartment buildings) in the area between the Castle Hill and the historic city core.