A legionary fortress at Valkenburg: discovering a springboard for the conquest of Britannia?

This article is from World Archaeology issue 108

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How often is a completely unknown Roman legionary fortress found? Very rarely, we would say. Yet this now appears to be the case at Valkenburg, in the Netherlands, where a major military base has been discovered. And what a base it is! This article describes step by step how this important new find came about, thanks to research at a former naval airbase undertaken by two Dutch archaeological companies (ADC ArcheoProjecten and Archol).

Excavating Valkenburg

Valkenburg is already renowned for its Roman archaeology, thanks to a military base that was excavated by A E van Giffen during and just after the Second World War. This fort held an auxiliary unit made up of soldiers recruited or conscripted from the occupied territories, who supported the Roman citizens serving in the legions, which were housed in much larger legionary fortresses. Valkenburg fort was made famous by the fantastic remains of timber and stone structures, which were preserved in the ‘wetlands’ of the western Netherlands. On the basis of the Tabula Peutingeriana – a medieval map believed to be copied from a Roman original – the fort may have been called Praetorium Agrippinae. Whatever the case, plenty of archaeological research has taken place in the vicinity of this fort over the last few decades. The investigated areas have toponyms like Veldzicht (investigated in 1994 and 1996-1997), Marktveld (1985-1988), Woerd (1972 and 1988), and Weerdkampen (2019), and they all lie to the south of the fort site, near the modern village of Valkenburg. Not all of the data from these explorations have, though, been scrutinised to the last sherd or soil discoloration, and in some cases work has largely stalled.

In 2010-2011, numerous trial trenches were opened on the western side of Valkenburg village, within the former naval airbase, and the results were published that same year. Various Roman structures were encountered during this work. Most striking was the combination of a number of V-shaped ditches, a dam or road, and a possible tower. One of the wooden posts supporting this apparent tower was set on a large block of wood that can be dendrochronologically dated to AD 39±6 years: a spectacular result. As we will see, quite a bit of Roman military activity was under way in the wider region during that period, so the date – together with the other finds – prompted much speculation. We believe this speculation has now come to a definitive end: the remains of a Roman legionary fortress have been found at the former naval airbase. This allows the history of Roman Valkenburg, and indeed that of the early Roman Netherlands, to be rewritten. Along the way, a gratifyingly large number of loose ends left over from earlier work can also be satisfactorily tied up.

Following the 2010-2011 work, it was suggested that the structures belonged to a temporary camp established during the reign of the emperor Caligula (37-41). The ancient literature records that Caligula planned to campaign in Germania when he left for the Rhine front in AD 39. We do not know his exact destination, but Mainz seems a likely candidate. Be that as it may, Caligula spent the winter in Lyon (Lugdunum), after which he apparently had a change of heart and Britannia hove into sight as a choice candidate for conquest. Ancient authors such as Suetonius and Cassius Dio describe how this desire descended into a bizarre farce after Caligula lined up his troops along the shore of ‘Oceanus’. The emperor briefly sailed forth in a ship, before returning and ordering his troops to collect seashells. This booty, which Caligula claimed as spoils of his triumph over the sea, was eventually taken back to Rome.

There is no call to rehearse all the detail of this extraordinary escapade here, but archaeologists have not ruled out the possibility that this event took place on the Dutch coast near Katwijk. Recent decades have furnished a number of suggestive finds, including the regular recovery of both struck and unstruck coins of Caligula, as well as barrels from Bunnik-Vechten and Valkenburg that bear the emperor’s official title. The ancient historian Tacitus also writes about a member of the Cananefatian group in AD 69 called Brinno, whose father had scorned Caligula’s campaigns with impunity. As we know that the Cananefates later inhabited this part of the North Sea coast, it might again suggest Caligula’s presence in the vicinity. None of this can be considered hard proof, of course, and some scholars favour different settings, but these considerations certainly fuel speculation about the location of these historical events.

Valkenburg revisited

It was against this backdrop that follow-up research at the naval airbase began in 2020. The plan was to learn more about the V-shaped ditches, in order to determine the size of the possible temporary camp. Connecting the known stretches of ditch suggested a large area was enclosed, but questions remained about whether all of these elements belonged to a single fortification. Our excavation trenches were laid at right angles to the ditches, in order to secure good cross-sections across them. As work progressed, we occasionally encountered what seemed to be structures to the east of the ditches. One example was a set of posts creating a structure that covered an area roughly 10m by 13m, positioned parallel to the ditch. This was surprising, to put it mildly, as temporary camps typically comprise little more than a bank and ditch, with the soldiers living in tents.