,'' 1809 In 297 Diocletian,
Augustus since 284, campaigned in Egypt to suppress the revolt of the usurper
Domitius Domitianus. After
a long siege, Diocletian captured Alexandria and executed Domitianus's successor
Aurelius Achilleus in 298. In 302 the emperor returned to the city and inaugurated a state grain supply. In the fourth century AD this designation also applied to Serapis, the male counterpart of
Isis in the pantheon instituted by the
Hellenistic rulers of
Egypt, the
Ptolemies. The sanctuary complex dedicated to Serapis in which the column was originally erected, the Serapeum, was built under King
Ptolemy III Euergetes in the third century BC and rebuilt under Roman rule, likely in the late 2nd to early 3rd century CE, being completed under Emperor
Caracalla. In the later fourth century AD it was considered by
Ammianus Marcellinus a marvel rivalled only by Rome's sanctuary to Jupiter
Optimus Maximus on the Capitoline Hill, the
Capitolium. The monument stands some high, including its base and
capital, and originally would have supported a statue some tall. The only known
monolithic column in
Roman Egypt (i.e., not composed of
drums), it is one of the
largest ancient monoliths and one of the
largest monolithic columns ever erected. The monolithic column shaft is in height with a diameter of at its base, and the socle itself is over tall. was confused with the Greek spelling of the
Republican general of the first century BC Pompey, ΠΟΜΠΗΙΟΣ (, ). The porphyry statue of Diocletian in armour is known from large fragments that existed at the column's foot in the eighteenth century AD. From the size of a fragment representing the thighs of the honorand, the original height of the
loricate statue has been calculated at approximately . While some fragments of the statue were known to be in European collections in the nineteenth century, their whereabouts were unknown by the 1930s and are presumed lost. It is possible that the large column supporting Diocletian's statue was accompanied by another column, or three smaller columns bearing statues of Diocletian's co-emperors, the
Augustus Maximian and the two
Caesares Constantius and
Galerius. If so, the group of column-statues would have commemorated the college of emperors of the
Tetrarchy instituted in Diocletian's reign. ==Ascents==