Taal is een tool

Minerva TXT producties - Portfolio | Minerva TXT producties

Eveline J. Verhoeve

Lid van VOA
Vereniging Ondernemingen Alphen eo

Lid van VNR
Vrouwen Netwerk Rijnstreek

Build for invading Britain

< Portfolio

The Roman castellum Albaniana in Germania Inferior

Eveline J. Verhoeve



The northern frontier of the Roman Empire is known as the Limes. It stretches from Britain to the Black See and runs roughly along a very old prehistoric trading route. A well known part on the main land runs along the river Rhine in the Roman province Germania Inferior. There a chain of fortresses was build to protect Roman interests. Until recently it was believed that the eldest castella in the western part of the province were build in 47 AD when general Corbvlo was ordered to guard the river Rhine as a new frontier. Now however it seems that the excavation results from the castellum Albaniana in modern Alphen aan den Rijn in the Netherlands proof that the first fortresses were build earlier in the year 40. The question is why? The answer seems to be: because Emperor Caligula really wanted to invade Britain and wanted to use the river Rhine for logistic reasons. This transportation route runs along the rivers Rhône, Saône and Rhine. And that means that Albaniana and the fortress in Valkenburg were not build, and probably the older fortress Fectio was not used to protect the Limes but to support an early invasion of Britain.

Rhine Frontier

Most scientific articles and books date the building of the Roman fortresses on the northern frontier in Germania Inferior in the year 47 AD. That was the year the Roman emperor Claudius ordered his general Corbvlo to retreat from Friesland which he was organizing as a new Roman province and to guard the river Rhine as the frontier instead. And most evidence from several excavation sites substantiates this point of view.

Valkenburg has been dated 39-41 AD based upon circumstantial evidence, which is good for building a theory but is not the same as solid scientific knowledge. Another peculiar thing about Valkenburg is its outline. Roman castella are all build the same way in the entire empire. But once and again somewhere there is something different and when there is there must be an explanation. But without more evidence it was difficult to investigate why this early outpost existed and why it looked different.


So far the situation in 1998. In that year the excavations in Alphen aan den Rijn started. The town needed a new centre and therefore the opportunity arose to excavate a long suspected archaeological site: a Roman castellum called Albaniana.

This castellum has been known to exist somewhere for a long time because it is mentioned on the Peutinger map between the fortresses of Nigrum Pullum (Zwammerdam) and Matilo (Leiderdorp) which were found and recorded. This map is a twelfth century copy of a fifth century Roman roadmap.

The existence of Roman remains described in 1714 by Plemper made it clear that somewhere in the centre of the little village Alphen there must have been something, so why not Albaniana? But that question was not answered for lack of interest from the scientific community and the regents of Alphen until 1920. Then there was a brief archaeological survey because of the burning of a church. That church turned out to have been built on the site of a Roman bathhouse situated outside the southern gate, as it turned out later, of the possible castellum.

During the next decades isolated Roman founds were reported; pieces of pottery, a bone comb, a tile… In the sixties substantial groundwork was done in the centre of town. Several findings were reported. But even when big new projects were executed no archaeological survey was conducted in spite of the artefacts that were found. So there were some clues that there must have been something in the centre of the town, but it was only after the discovery of Nigrum Pullum (excavated in 1968-1974) which belongs to the same council as Alphen aan den Rijn that the possibility of another important castellum was really taken seriously.


The excavations that started in 1998 and were finished in 2002 revealed a castellum of a very early date, at an unusual spot and with an unusual outline. It just was not in line with all the other Roman fortresses. Except for one: Valkenburg. And Valkenburg was the only other example of this type. The explanation turned out to be sensational: Albaniana was not build to guard the northern frontier after general Corbvlo retrieved behind the barrier of the river Rhine in 47 AD, but this fortress was build to enable the emperor Caligula to invade Britain in 40 AD and so was Valkenburg.

The invasion of Britain by Caligula never happened and it has turned into a bit of a joke by history. But there are serious indications that Caligula was really planning and preparing for the invasion. Why he chickened out on the beach before making the crossing from France is a bit mystified but evidence of a lot of real preparations exists. With the excavation results of Albaniana there are even more.


The dating of Albaniana turned out to be not that difficult. Because of the very wet soil conditions – the biggest part of the Dutch province Holland were Alphen aan den Rijn is situated, is peat and back then that meant swampy – many artefacts were protected and therefore survived two millennia under the ground. In the end 700 coins, 27.000 fragments of pottery, 5000 pieces of metal and several hundreds of kilos of bone, brick and artefacts of masonry were found. And a lot of datable wood as well…

Most of the coins – 324 out of 750 - are dated during Caligula’s reign (37-41 AD) and were not marked by his successor Claudius. That means that it is the current money and not that of a former emperor. So, those unmarked coins were most likely used and lost when Caligula still was emperor. The rest of the coins date from another few hundred years until the castellum was abandoned in 270 AD.

Very datable even within a season are the many pieces of wood which were found in the wet ground. In the case of Valkenburg only one dendrochronological survey lead to the conclusion that at least one tree was used which fell in 40-41 AD. A dendrochronological survey is based on counting year rings; trees grow different every year and every season and if there are enough examples it is possible to build a solid timeline. The first of the several fortresses at the site Albaniana was dated by a lot of wood. And over and over again there was the same conclusion: here was another fortress that was build in the winter of 40-41 AD under the reign of Caligula.

Transport route

Which raises the question why? What did Caligula gain from building a fortress along a river in a swamp in an area that was managed fine by one of his generals? For Corbvlo was doing a good job in pacifying the tribe of the Fries and organizing the northern part of Germania Inferior. The answer lies in planning the long awaited invasion of Britain. After Caesars first visit Britain was left but not forgotten. So Caligula intended to rule overseas as well.

He managed to build a large military force and gathered them on a beach near Boulogne. But for whatever reason he did not cross the Channel but went home instead. Meanwhile he had ordered an infrastructure to enable him to support his troops during and especially after the crossing. The route these transport ships took was different from that of the troops. The transports used the rivers Rhône, Saône and Rhine. So at the end of that route protection was needed and therefore some castella along the river Rhine. And that’s why most likely the building of the fortresses Albaniana and Valkenburg started.


The explanation for sustaining those early fortresses although the invasion was aborted is one of reasoning. This can not (yet) be proven. Claudius succeeded in 43 AD in invading Britain. He might only have been able to do so at such short notice - he became emperor in 41 AD – because he could use some infrastructure of his predecessor.

Another reason may lie in Caligula’s bad temper. He was difficult, cruel, short-tempered and went into history as an unpredictable monster. Often his generals received conflicting orders and it is suspected that they did a lot on their own just to save their heads. So when the order came to build some fortresses along the river Rhine, the building of the castella of Valkenburg en Albaniana were started as was a raised activity in Fectio. When a year later the order came to abandon the work it now seems very likely the building went on and Emperor Claudius profited by the existence of those fortresses in 43 AD when Britain wás invaded.

When sailing from the estuary of the Rhine to Britain it is likely to arrive in the estuary of the river Thames. Whether Claudius actually spread his troops between the south coast and the Thames is an ongoing debate between English scholars. The excavation results from Albaniana support the theory that Claudius indeed split up his supplies and possibly his troops.

Lay out

Another proof for the theory that the reason for building Albaniana has to do with invading Britain is the peculiar outline of the castellum. From the writings of Vegetius, a fourth century Roman military expert, it is clear that there are rules to follow when building a castellum.

Vegetius says that building on high ground is preferable; it is dry, has a good view and is therefore easily defendable. Albaniana was built on the edge of a swamp along the riverside. Everybody must have had constantly wet feet and the camp site overflowed on a regular basis; conditions were severe. This still relative dry land near the river was very narrow. Between the camp site and a sandy island of high ground only 300 meters away was a real swamp.

The high ground would have suited the Roman legionnaires much better. Why not build there? That must have had something to do with the importance of being close to the river. Indeed; the fortress is ideally situated for guarding the river because one of the long sides faces the waterfront.

Vegetius also gave the rules for the general outlay of a camp site or a fortress. In theory every Roman soldier would have known were to find a latrina in pitch dark in every camp site in the entire empire. But again, Albaniana (and Valkenburg) is different. In stead of a square the outlay is a trapezium and the number of buildings is also different. The main gate is facing the waterfront and the main road divides the fortress into two narrow strips. Thus it was just squeezed in between the water and the swamp. Again; ideal for guarding everything that went on on the river.


In those early years the nearest castella were Valkenburg (build in the same year), Velsen situated in the estuary of a northern arm of the Rhine and Fectio. The other fortresses were built when work on the Limes started in 47 and later. That meant that the distance between castella was larger than suitable for easy supplies. So on top of the severe conditions the legionnaires had to provide for themselves. That resulted in an extremely large fabrica – workplace - from which many artefacts remain.

The question was of course the other way round: why did Albaniana within a chain of fortresses along the Limes need such a large fabrica? Well, because there was no chain yet and because of the invasion of Britain.


This article is based on:

a lecture and handout by Prof.dr. M. Polak in September 2004 on the occasion of presenting the second part of the results of the excavations in Alphen aan den Rijn to the council in Themepark Archeon;
a lecture by P.F.J. Franzen in 2003 in CBK in Alphen aan den Rijn;
J.K. Haalebos, P.F.J. Franzen ea, Alphen aan den Rijn-Albaniana 1998-1999, Nijmegen 2000;
R.S. Kok, Archeologische inventarisatie Stadshart Alphen aan den Rijn, Alphen aan den Rijn 1999;
M. Polak, R.P.J. Kloosterman & R.A.J. Niemeijer, Alphen aan den Rijn-Albaniana 2001-2002. Opgravingen tussen de Castellumstraat, het Omloopkanaal en de Oude Rijn, Nijmegen 2004.

First published in 2004/2005 on the British website Legio Secvnda Avgvsta

< Portfolio

Volg mij op...