Ancient Lisbon: Romans, Moors and the Layers Beneath Your Feet

Lisbon did not begin with trams, the Age of Discoveries or even the castle on the hill. Before the Christian city, before Pombaline Baixa and long before the modern avenues, there were Roman Olisipo and Islamic al-Ushbuna. Both are still present, not always in plain sight, but close enough to the surface to change how you walk through the city.

The best way to understand ancient Lisbon is to accept that it appears in fragments. A wall near the castle, a ruin beneath a building, a crooked street in Alfama, an object in a museum. The city has been built over itself for centuries, with each period reusing, erasing or covering the one before it.

Olisipo, the Roman city

Under Roman rule, Lisbon was called Olisipo and held an important position at the western edge of the empire. Its location mattered: a natural harbour on the Tagus, access to the Atlantic, defensible hills and links to trade routes. It was not Rome in miniature, but it had a theatre, baths, a forum, roads and an organised urban life.

The clearest site to visit is the Roman Theatre, on the slope between the cathedral and the castle. The ruins were discovered in the eighteenth century after the earthquake and now form part of the Museu de Lisboa. The theatre was built in the first century and used the natural slope of the hill. Enough survives to imagine seating, stage and an audience facing the lower city and the river.

The museum is small, but it gives the site useful context. Do not expect a monumental ruin on the scale of Mérida or Rome. The power of the place lies in the contrast: Roman stones embedded in an ordinary Lisbon street, with lived-in buildings around them and the cathedral a few steps away.

What lies under Baixa

Much of Roman Lisbon is buried. In Baixa, excavations have revealed ancient structures in basements, construction sites and protected spaces. The best-known example is the Roman Galleries of Rua da Prata, underground structures that open to the public only on specific occasions for technical and safety reasons.

Even when you cannot go inside, knowing they exist changes how the city reads. The Baixa that looks so clearly Pombaline rests on earlier layers. The same is true across Lisbon, where private and public works still uncover ceramics, walls and pavements. Ancient Lisbon rarely appears complete. It comes up in pieces.

The Moorish city

After the Roman and Visigothic periods, Lisbon belonged to the Islamic world for more than four centuries. The Muslim city, known as al-Ushbuna, occupied mainly the castle hill and the slopes of Alfama and Mouraria. It was a walled city connected to the river and shaped by narrow streets adapted to the terrain.

Castelo de São Jorge preserves part of that memory. The walls visible today belong to several phases, including later rebuilding, but the hill was central to the defence of Islamic Lisbon. Walk around the castle, especially away from the busiest viewpoints, and the defensive logic becomes clear: control of the river, control of access points and protection of the slopes.

Mouraria and Alfama

Mouraria takes its name from the district where the Muslim population was concentrated after the Christian conquest of 1147. The neighbourhood has changed enormously since then, but the name matters. It does not mean that every current street is a direct survival from the twelfth century. It means this area carried the social and cultural mark of that past for centuries.

In Alfama, the irregular layout, steps and alleys are often linked to the Islamic city. Be careful with easy certainties: Lisbon has been rebuilt, altered, opened, closed and patched across many periods. Still, Alfama preserves an urban scale that helps you imagine pre-modern Lisbon far better than Baixa's grid.

Where to see the layers

For a simple route, start at the Roman Theatre, climb to the cathedral, continue to the castle and descend through Alfama or Mouraria. Add the Museu de Lisboa when you can, for objects, maps and archaeological context. If the Roman Galleries are open for a special visit, treat it as a rare opportunity and confirm dates through official channels.

The key is not to expect a clean narrative. Roman Lisbon is not contained in one monument. Moorish Lisbon is not either. Both appear through scattered signs, often mixed with Christian buildings, Pombaline reconstruction and daily life.

That is precisely what makes the city rich. Beneath every postcard is an earlier Lisbon. Beneath that, another one. When you climb from Alfama to the castle or descend from the cathedral towards Baixa, you are crossing more than neighbourhoods. You are crossing layers of occupation, language, religion, trade and power that still shape the streets, even when no sign names them.