The Catacombs of Kom el-Shoqafa

Kom el-Shoqafa is in the Karmouz district of Alexandria, a few minutes from Pompey's Pillar. Nothing much shows at street level. You go down.

A spiral staircase winds around an open central shaft, which was used to lower the dead, and descends past three levels cut into the rock. The lowest is flooded and closed.

The main tomb chamber is one of the strangest things in Egypt, and the strangeness is the point. Alexandria under Rome was a city where Egyptian, Greek and Roman worlds were fully mixed, and here somebody carved all three into one small room without apparently feeling any conflict. Egyptian gods stand in Greek proportion and Roman dress. Anubis appears in the armour of a Roman legionary, with a sword and a cloak, and keeps his jackal head.

The doorway of the burial chamber is flanked by two great serpents wearing the double crown of Egypt and carrying a Greek caduceus and thyrsus, with round Medusa shields above them. Egyptian protective serpent, Greek attributes, Roman shield — one doorway, three cultures, no seam.

There is also the triclinium: a rock-cut dining room with stone couches around three sides, where the family came down to eat a funerary banquet with their dead. The cups and plates they left behind gave the site its Arabic name, which means mound of shards.

The tomb dates to around the second century AD and began as a private family burial, then expanded over time as more chambers were cut around it and it took in more bodies.

It came to light in 1900, and the traditional account is that a cart animal broke through into the shaft. Excavation followed immediately.

One adjoining space, usually called the Hall of Caracalla, contained a quantity of human and horse bones. The name attaches it to the massacre the emperor Caracalla is said to have carried out in Alexandria, though that connection is a tradition rather than an established fact.

The flooding of the lowest level is Alexandria's oldest enemy at work: the city has been subsiding for two thousand years and groundwater rises through the rock. A conservation project in recent years installed pumping to hold the water table down, which is what keeps the second level dry and open.

Kom el-Shoqafa is also shorthand for a larger truth about Alexandria: almost nothing of the ancient city survives above ground. The palaces and the Library are gone, under the sea or under the streets; what remains is what was cut downward into rock — cisterns, tombs, foundations. Alexandria's antiquity is underground.

• The main burial chamber, with Egyptian gods in classical style
• Anubis carved in Roman legionary armour
• The serpents and Medusa shields flanking the chamber door
• The spiral stair around the open body shaft
• The loculi — burial slots cut by the dozen into every passage wall
• The triclinium with its rock-cut banqueting couches