Atuatuca (or Aduatuca) was the name of one or more fortified settlements in the region between the Scheldt and Rhine rivers, during the "Gallic wars" of Julius Caesar. The word itself possibly meant "fortress". The pronunciation "Atuatuca" with a "t" is considered to be the original, despite many Latin documents using a "d". The modern city of Tongeren, referred to as Aduatuca Tungrorum in later Roman imperial times, is at least one of these places, and if there were more places with this same name they were all in the same general region to the north of the Ardennes, and in or near eastern Belgium. At the time, this region was inhabited mainly by the Eburones.
Apart from later mentions of this placename which clearly refer to Tongeren, Caesar's commentaries on his wars in Gaul are the only surviving source of information. His first mention of "Aduatuca" by name, during discussion of his suppression of an Eburone rebellion, and subsequent involvement by Sigambri from Germany, says that it "is the name of a fort. [Id castelli nomen est. This could also mean it is the name for a fort.] This is nearly in the middle of the Eburones, where Titurius and Aurunculeius had been quartered for the purpose of wintering." He was referring to earlier sections of the commentaries where Q. Titurius Sabinus and L. Aurunculeius Cotta where slain during the start of this rebellion of the Eburones. These two lieutenants of Caesar had been ordered to winter amongst the Eburones after a drought year, which was a cause of the rebellion, although Aduatuca had not been named in the earlier discussion.
Unfortunately, although Caesar says the fort was in the middle of the territory of the Eburones, there is no consensus on the boundaries of the Eburone territory. At one point Caesar says that the chief part of the territory of the Eburones was between the Mosa (Maas or Meuse) and the Rhine. But it is generally agreed that the Eburone territory also included land between the Scheldt and the Maas, including all or most of the low-lying "Campine".
Caesar described the surrounding area as a place where the Eburones were able to disperse dangerously; some, including the Eburone leader Ambiorix, apparently into remote parts of the Ardennes, and others towards tidal islands in the Ocean. There was "no regular army, nor a town, nor a garrison which could defend itself by arms; but the people were scattered in all directions. Where either a hidden valley, or a woody spot, or a difficult morass furnished any hope of protection or of security to any one, there he had fixed himself".
Several arguments have been given for interpreting the name Atuatuca to mean fortress, and not to be the same as Tongeren.
Apart from Tongeren, proposals concerning the location of this earlier Atuatuca of the Eburones include Spa (at a place called Balmoral) and Caestert at the place Kanne, just south of Maastricht, and reasonably close to Tongeren.Dendrochronological evidence was once thought to count against this proposal, but more recent review of the evidence has reinvigorated the idea.
Other proposed sites in the nearby Liège province include Battice, Limbourg, Dolembreux, northeast of Esneux and Chaudfontaine; as well as Thuin, in Hainaut province. In Germany, Atsch in Stolberg, near Aachen, as well as the Ichenberg hill near Eschweiler have also been proposed.