Architecture of the Casbah of Algiers

The old city is a triangle running down to the water, and it is steep the whole way. The summit stands about a hundred and eighteen metres above the sea. UNESCO inscribed 54.7 hectares of it in 1992 under criteria ii and v, as a unique kind of medina and as an outstanding example of a traditional human settlement.

Because the ground falls away continuously, no house blocks the one behind it. The Aga Khan Documentation Centre describes the result as interlocking masses of white geometric houses with roof terraces turned towards the bay. Every dwelling gets the sea, and it gets it from the roof rather than the window.

The streets follow the same logic. They are tortuous and interconnected, some no wider than a corridor, others vaulted over like cellars. Climbing towards the upper Casbah they narrow further and turn into stairs, because stairs are the only honest way to take that gradient. Where an upper room bridges an alley the street simply runs through the building, under a covered passage called a sabbat.

The flat part of the city did not survive. The lower Casbah was demolished in stages between roughly 1832 and 1913 to make room for the colonial port city. What is left standing is what was too steep to be worth clearing, which is why the medieval street plan is still there to walk.

The typical dwelling is a compact, highly introverted structure of about three storeys. From the alley it gives almost nothing away: a blank rendered wall, one door, and very little else. Everything the house has to offer is behind that wall.

Inside the door is the sqifa, a room where male visitors were received precisely so that they would not go any further. It is a filter, not a hallway. Past it the house opens into the wast ed-dar, the middle of the house, the courtyard that is the main source of daylight and fresh air for every room around it. Galleries on each floor run round the courtyard and carry the circulation, so that the domestic life of the household happens in the open air without ever being visible from outside.

The sequence is deliberate and it is the best thing about the building. You come in from a bright, hard, narrow street into a dark low room, and then out again into a tall shaft of light with water at the bottom of it. The contrast is the architecture. Researchers who have studied the experience of moving through these houses describe it in exactly those terms, as an alternation of openness and closure, light and shadow, low and high.

The dimensions come from the body rather than from a drawing board. A house of this kind is set out to the pace of a step and the height of a shoulder, which is why the rooms feel correct without being regular, and why no two of them are quite the same size.

The roofs are not roofs. They are flat terraces, they are on much the same level as their neighbours, and they are connected. The Aga Khan Documentation Centre records residents moving from house to house across them and bypassing the street entirely.

That mattered socially before it mattered militarily. The street was public and effectively male; the house and the terrace were private and effectively female, and the terrace network gave women a whole upper storey of the city to move and talk across without ever appearing at street level. Each terrace, and especially those near the summit, also holds a view over the entire city and the sea.

It is worth noticing what this means structurally. The Casbah has two circulation systems stacked on top of each other, one at the bottom for strangers and trade, one at the top for households. Very few cities anywhere have ever had that, and the ones that did mostly lost it. If you want the consequences of it, they are on the history page.

UNESCO lists the materials of the Casbah plainly: earthen bricks, earthen and lime rendering, stone and wood. There is nothing exotic in that list. All of it came from within a few kilometres, and the sophistication is in how it was used rather than in what it was.

Research published in 2026 makes the point precisely. A team examining the building limestones of the Casbah identified three different stones, all from Upper Pliocene outcrops ringing the city, and found that each had been matched to a particular job: a compact rhodalgal limestone for refined architectural elements, a softer sandy limestone for ordinary masonry, and a pale brown calcarenite in later repair work. The builders were not simply taking whatever came out of the nearest quarry. They were selecting.

Over all of it goes lime. The render is what gives the Casbah the appearance that earned Algiers the name of the white city, and it is not only cosmetic: a lime coat sheds water, lets the wall behind it breathe, and is cheap enough to renew.

The other thing shaping these walls is the ground itself. Algiers sits in an active seismic zone, and after the earthquake of 1716 the authorities imposed earthquake-resistant requirements on the rebuilding of the city, affecting both the layout of streets and the construction of individual houses. That episode is studied today as an early and deliberate example of seismic building rules, worked out three centuries before the codes we now take for granted.

The arch of Algiers is a pointed horseshoe: the curve carries past the halfway line and then rises to a point. Ranged in a gallery, four to a side, it produces the rhythm that reads instantly as this city and not Fez, Tunis or Cairo.

The columns under those arches are often wreathed, their shafts twisted like rope, and they carry composite capitals. At Dar Mustapha Pacha the capitals are decorated with crescents. Floors are laid in marble hexagons. The lower part of the wall, the part a person leans against or a child touches, is faced in glazed tilework, and niches are tiled to match.

That is the rule the whole quarter follows. Ornament is applied where the body meets the building, which means at eye level and below, on the courtyard wall, on the stair, on the door leaf and around the openings. The street face gets none of it. A restorer working at the Palace of the Raïs in the 1990s had to reproduce faience cladding, carved woodwork, wrought iron grilles, marble and corbels to put a facade back, and every one of those elements belongs to the inside of a building, not the outside.

There is no separate grammar for the grand buildings. A palace in Algiers is a dar, a house, and it is put together the way a modest house is put together, with more money spent per square metre.

Dar Mustapha Pacha, built between 1798 and 1800 for the dey of that name, is the clearest surviving example, and one of the rare palaces that came through the French occupation without major alteration. Three vaulted vestibules lead to a central courtyard of 9.5 metres square with an octagonal fountain at its centre. Two levels of galleries surround it on all four sides, four pointed horseshoe arches to each side. The whole building covers 709 square metres, and it has held the national museum of illumination, miniature and calligraphy since 2007.

Compare that with the ordinary house and the parts are identical: an entrance sequence that turns before it arrives, a courtyard at the centre, galleries on every floor, decoration concentrated low and inside. The palace has a fountain where the house has a well, and marble where the house has fired tile.

The Palace of the Raïs, known as Bastion 23, shows the same arrangement at the waterline. Built in the sixteenth century under Ramdan and Mustafa Pasha, it is a complex of four palaces and several houses covering more than half a hectare on the seafront, lived in by the raïs, the captains, and by the people who worked the port. It survived the demolition of the marine quarter, which almost nothing else did, and was restored through the late 1980s and 1990s.

This is the part that should be stated in numbers rather than adjectives. In 1962 there were around twelve hundred traditional buildings in the Casbah. Thirty years later, in 1992, the year of the UNESCO inscription, about four hundred dwellings were still standing. Roughly fifty came down in the four years between 1975 and 1979 alone.

The public buildings went the same way. A quarter that once had a hundred and thirty mosques and eighteen zaouias was down to ten mosques and two zaouias. Of about a hundred hammams, six remained.

Meanwhile the population went up. Density in several districts reached four thousand people per hectare, among the highest figures recorded anywhere in the world, with single-family courtyard houses divided between several households at a time. A building designed around one family, one courtyard and one well does not behave well with six families in it.

Counts differ depending on what is being counted, and it is worth saying so rather than picking the convenient figure: the Aga Khan Documentation Centre still describes roughly twelve hundred houses in the old city, where the 2012 survey quoted above counted four hundred surviving dwellings of the traditional type. The two are measuring different things.

The structural point is the one that gets missed. This is a continuous fabric of shared walls on a slope. A house here is not a free-standing object that can fail on its own. When one goes, it takes away the support of whatever was leaning on it, and the loss is never confined to the plot it happened on. That is why a collapse in the Casbah is a different kind of event from a collapse anywhere else, and why repair has to be thought of by the block rather than by the building.