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History · Chapter I27 BC – 6th c.

Aeminium, Roman Coimbra

Baixa← west · the Alta hill in section · east →Alta

Before it was Coimbra, the Roman city was called Aeminium. The ground the Romans built for the main square is still there — beneath the Machado de Castro National Museum, on the slope that runs down to the Mondego.

How to read the stamps
  • Measuredread today by instrument
  • Excavatedfound in excavation and published
  • Documentedwritten in an ancient source or a record
  • Hypothesisproposed by researchers, not proven
  • Diagrama drawing to explain, not to the scale of the find
THE SECTION

How to build a square on a slope

The Alta hill cut in half, from the river to the top. Close up, at the same scale horizontally and vertically.

  1. 01

    A line through the hill

    Cut the city in half along a straight line from west to east: from the left bank of the Mondego, through the Baixa, up to the top of the Alta.

    The line passes through the Machado de Castro National Museum. Above the ground, today’s rooftops.

    Measured[2]
  2. 02

    Take the city away

    Without the buildings, the ground is left. The Baixa is flat, almost at river level. Then, the hill.

    From the Baixa to the museum courtyard the ground rises 70 metres, almost all of it in the last 270 metres of the way.

    Measured[2]
  3. 03

    A square does not fit on a slope

    In the time of Augustus, the Romans placed the centre of Aeminium at the top of this hill. The centre of a Roman city is the forum: a flat square, with porticoes, the basilica and the temples around it.

    The ground there was very steep. To have a square, the ground had to be built.

    Excavated[1]
  4. 04

    So the ground was built

    Against the slope rose a cryptoporticus: two storeys of closed, vaulted galleries holding up a level platform. From outside, a tall, plain podium, with only slits to let in air and light.

    On the west side, the tallest, the façade stood about 29 metres high.

    Excavated[1]Diagram
  5. 05

    On top, the square

    On the platform sat the forum, with a two-storey portico. On the west façade the portico opened in arcades, like the Tabularium in Rome.

    From there you could see over the city’s rooftops and, further off, the Mondego and the slope of the far bank.

    Excavated[1]Diagram
  6. 06

    The forum went. The ground stayed

    By the end of the 11th century nothing was left of the forum; on top of the cryptoporticus stood the bishop’s palace. The palace was rebuilt over the centuries and, at the beginning of the 20th century, became a museum.

    The cryptoporticus survived whole, except for the west façade. The museum courtyard corresponds, roughly, to the old square.

    Excavated[1]
INSIDE THE CRYPTOPORTICUS

Fourteen cells beneath the square

Two storeys of closed, vaulted galleries, with only slits for air and light. Inside, this is how they are laid out.

upper floorlower floorgallerydiagram · not to scale

Above. Two P-shaped galleries, one wrapped around the other, with barrel vaults. Between the arms of the P, seven cells linked by narrow passages.

Below. Beneath the seven upper cells, another seven, longer and taller, opening onto a long gallery.

Excavated[1]Diagram

Who designed it

One Gaius Sevius Lupus, “architect of Aeminium”, left a dedication to Mars beside the Roman lighthouse at A Coruña, the Tower of Hercules. He may have been the author of the forum — there are similar construction details in both.

Hypothesis[1]

A swapped face

Portraits of Livia, Agrippina the Elder and Nero come from the forum. Nero’s was later recarved with the face of Vespasian; then a Trajan joined the gallery.

Excavated[1]
IN LAYERS

Two thousand years, from top to bottom

It reads the way you dig: the most recent at the surface, Augustus at the bottom.

surface · today’s city
  1. 1992 – 2008

    Digging beneath the museum

    The works to refurbish and extend the museum were preceded and accompanied by excavations over about 750 m². Almost everything known about the forum comes from them.

    Excavated[1]
  2. Early 20th c.

    The palace becomes a museum

    The episcopal palace is converted into what is today the Machado de Castro National Museum.

    Documented[1]
  3. Late 16th c.

    A loggia like the Roman one

    The palace gains a loggia that adopts a solution similar to that of the Roman portico, fifteen centuries later.

    Documented[1]
  4. 14th c.

    The west façade falls

    The only part of the cryptoporticus that has not survived. It may have fallen in earthquakes.

    Hypothesis[1]
  5. Late 11th c.

    A palace on the cryptoporticus

    Nothing of the forum remains above ground. On top of the Roman galleries stands the episcopal palace.

    Excavated[1]
  6. 6th c.

    Aeminium becomes Coimbra

    After the Suebi attacked Conímbriga, between 465 and 468, the city grows with those who flee from there — and ends up inheriting its neighbour’s name.

    Documented[4]
  7. 1st c.

    Pliny writes the name

    In his Natural History, Pliny the Elder puts the Aeminienses on the list of the stipendiary cities of Lusitania — those that paid tribute to Rome.

    Documented[1]
  8. 41 – 68

    The forum is rebuilt from scratch

    It begins under Claudius and ends under Nero. The Augustan cryptoporticus is embedded in another, much larger one. The date comes from the pottery found in the construction layers.

    Excavated[1]
  9. 27 BC – AD 14

    The first forum

    In the time of Augustus, the city already has a forum and a smaller cryptoporticus: a single vaulted aisle, with five doors opening onto a terrace to the west.

    Excavated[1]

The cryptoporticus can be visited.The entrance is through the Machado de Castro National Museum.

Opening hours and tickets on the museum’s website →
References
  1. J. de Alarcão, P. C. Carvalho and R. C. da Silva (2017), “The forums of Conimbriga and Aeminium: comparison and summary of the state of the art”, Zephyrus LXXX, pp. 131–146. doi.org/10.14201/zephyrus201780131146
  2. Direção-Geral do Território, LiDAR digital terrain and surface models, 2 m (2024). cdd.dgterritorio.gov.pt
  3. Building and water outlines: OpenStreetMap contributors (ODbL). www.openstreetmap.org/copyright
  4. “Aeminium, a antiga cidade romana de Coimbra, de que hoje só restam vestígios”, Observador, 8 February 2016. observador.pt/2016/02/08/aeminium-antiga-cidade-romana-coimbra-hoje-so-restam-vestigios