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The harbour of Trajan

The wide and shallow expanse of water in Claudius' basin may have been vulnerable, witness the events of 62 AD. This may have been one of the reasons why Trajan built a second, hexagonal basin behind the basin of Claudius. The work was carried out in the years 100-112 AD, and included improvements of the Claudian harbour. The capacity of the harbour was much greater now, and many new warehouses were built around it. The sides of the hexagonal basin measure 357.77 metres, perhaps 1200 Roman feet. The maximum diameter is 715.54 metres. It was five metres deep. The bottom was covered with stones, at the north end gradually sloping upwards, to reach a depth of only one metre at the edge of the basin. On the quays were travertine blocks with holes, used for mooring, fifteen metres apart (h. 1.10, w. 0.75, d. 2.0, diam. of holes 0.45).

A mooring block. Testaguzza 1970, p. 104.

The basin could contain more than 100 ships that did not moor alongside the quays, but at a straight angle. It was surrounded by a few wide treads (total width c. 6 m.). Numbered columns with Latin numerals were also found around the basin, suggesting that the sides of the hexagon were subdivided into numbered sectors. On the quays was a wall, with five narrow doorways (1.80) on each side of the hexagon. The doorways are too narrow for wagons. Apparently the goods were unloaded and carried by slaves. This can also be seen on several reliefs and mosaics. The wall facilitated the control of the flow of goods, for the Customs Service and the levying of import duties (the portorium).

The hexagon may have been designed by Apollodorus of Damascus, the architect of Trajan's Market in Rome. No other harbours are known with this shape, suggesting that it was chosen not only for practical purposes, but also for aesthetic reasons, emphasizing the power of Rome and the Emperor.

A Trajanic coin of the hexagonal basin.

A badly preserved inscription from the years 102-109 AD (Thylander B312) mentions Trajan, a channel and inundations of the Tiber:

[imp caes divi]
NE[rvae f nerva]
TRA[ianus aug germ]
DAC[icus trib pot]
I[mp cos pp]
FOSSAM [fecit]
[q]VA INVN[dationes Tiberis]
[ad]SIDVE V[rbem vexantes]
[rivo p]EREN[ni instituto arcerentur]

It may well be this channel that was that was identified by Keay (2005). He found a curved channel, now filled in, in the south-east part of Portus. It was c. 35 metres wide and connected the Tiber and the Claudian "Fossa Traiana". It was flanked by towpaths.

This harbour was called Portus Traiani or Portus Traiani Felicis. The harbours of Claudius and Trajan together were called Portus Augusti et Traiani Felicis, but also Portus Uterque ("Both Harbours").

Domus and ground-floor apartments have not yet been found in Portus. Many people working in Portus may have lived in Ostia (Portus was until the early third century AD part of Ostia), but in the later second century Galenus wrote that both Ostia and Portus were populous centres. The habitations were probably for the most part located to the south of the hexagon. The size of the population may have been in the order of ten thousand. Thousands of slaves must have worked in the harbour. Perhaps they lived on the upper floors of horrea, or outside the city.

Trajan's basin. Click on the photo for a larger image.
Photograph: Jan Theo Bakker.

[jthb - 6-May-2009]