The bridge Rome demolished

Chapter

100 – 103

The gorge road

c.100

The river today

800 m wide

Murray's depth

18 feet

Around 100, while the legions cut a military road along the Iron Gates gorge – the work the Tabula Traiana inscription commemorates – Trajan's staff faced the harder problem: the Danube itself. The road could march an army to the river; only a bridge could march it across.

Dio's description is the whole ancient survey we have: twenty piers set in a river 'so deep', in water 'so full of eddies', on 'a bottom so muddy' that diverting the stream was impossible. The engineers chose the narrowest practicable point – and paid for it, because the contracted current ran all the more violent and deep.

Today the Danube is 800 metres wide at the site, and the ancient depth is undocumented: Dio gives words, not numbers. The only figure ever attached to the spot is a modern one – Murray's Handbook, about 1875, sounding 18 feet – and the Iron Gates dams of 1972 and 1984 have turned the whole reach into a reservoir since.

How, then, could one fail to be astonished at the way in which each of them was placed in a river so deep, in water so full of eddies, and on a bottom so muddy? For it was impossible, of course, to divert the stream anywhere.

Cassius Dio 68.13 (Cary transl., 1925)

Meanwhile While the engineers sounded the narrows, the road gangs were still cutting Trajan's highway through the gorge below.

Chapter

103 – 105

Built

103–105

Total length

1,135 m

Piers

20 of stone

Between the spring of 103 and the spring of 105, Apollodorus of Damascus – the architect of the Column – spanned the Lower Danube east of the Iron Gates. The purpose was blunt: to carry Trajan's troops and supplies into the Second Dacian War against Decebalus.

Dio counted twenty piers of squared stone, 150 feet high above their foundations and 60 wide, standing 170 feet apart and joined by arches. Modern convention renders the whole as 1,135 metres long, 15 wide and 19 high above the water, with 38-metre wooden arches on brick-and-pozzolana masonry; each pier rose inside its own wooden caisson, and a fort guarded each end.

The bricks still found around Kostol name the builders: the legions IV Flavia Felix, VII Claudia, V Macedonica and XIII Gemina, with the cohorts I Cretum, II Hispanorum, III Brittonum and I Antiochensium. Their stamps are the site's muster roll, two thousand years on.

Trajan constructed over the Ister a stone bridge for which I cannot sufficiently admire him. Brilliant, indeed, as are his other achievements, yet this surpasses them.

Cassius Dio 68.13 (Cary transl., 1925)

Meanwhile The bridge was finished in 105; the Second Dacian War it served ran 105–106 and ended with Dacia a province.

Chapter

117 – 138

Hadrian reigns

117–138

Superstructure

removed

Piers in Dio's day

still standing

At some point in Hadrian's reign – no source gives the year – the wooden superstructure came down. Dio states the reason as plainly as a dispatch: Trajan had built the bridge fearing war across a frozen Danube, and Hadrian feared the same road in reverse, once barbarians overpowered its guard, carrying invasion into Moesia.

The Romanian account names the pressure on the frontier: the Roxolani and the Iazyges. One late report says the superstructure was destroyed by fire; the rest was abandonment, completed when Rome finally gave up Dacia in 275.

Only the timber went. Dio, writing a century later, found the stone piers still standing and the crossing gone – monuments, as he put it, to the proposition that human ingenuity can accomplish anything.

Hadrian, on the contrary, was afraid that it might also make it easy for the barbarians, once they had overpowered the guard at the bridge, to cross into Moesia, and so he removed the superstructure.

Cassius Dio 68.13 (Cary transl., 1925)

Meanwhile Seven years after the Second Dacian War, on 12 May 113, Trajan dedicated the Column that still tells the bridge's story – the sister project.

Chapter

1689 – 1984

Marsigli surveys

1689

Piers mapped, 1982

12 under water

Iron Gate II

1984

In 1689 the Habsburg engineer Luigi Ferdinando Marsigli surveyed the remains stone by stone and dreamed, unsuccessfully, of raising a new bridge beside them. His Danubius Pannonico-Mysicus of 1726 preserves the piers as the river left them; writing from personal observation, he gave the total length as probably 3,010 feet.

The nineteenth century watched the count fall. Thirteen piers still showed about 1875; a record low water in the 1850s – 1856 in the Romanian article, 1858 in the English, the year genuinely disputed – bared all twenty; the Danube Commission destroyed two pillars in 1906, sixteen remained under water in 1932, and twelve were mapped in 1982, four probably swept away.

Then the dams rewrote the river: Iron Gate I in 1972, Iron Gate II in 1984, the valley drowned into a reservoir and the water up 35 metres near the dam. A 2003 underwater survey fixed the state of what survives; today the two entrance piers stand on their banks – the northern one in a concrete compound – and both states list the bridge as protected heritage.

The one point as to which it gives clear information, not supplied elsewhere, is that the superstructure was of wood.

Encyclopaedia Britannica, 9th ed., IV.373 (c.1875)

Meanwhile In 1972, while the reservoir rose 35 metres near the dam, the Tabula Traiana was lifted clear of the drowning gorge.