The remarkable structure known as the 'Elliptical Building' stood in the central division of the legionary fortress of Deva , occupying most of the insula lying to the dextral rear (north-west) of the headquarters building ( principia ). Partially uncovered in 1939, the remainder was exposed during rescue excavations in the late 1960's which also revealed the presence of a small bath-house occupying the southern end of the insula. A report on this building has now been compiled by the present writer in Chester Archaeology`s Monograph series, and includes versions of the computer-graphics reconstructions shown here prepared by Julian Baum.

The precise function of this building is unknown as work on it was abandoned well before completion, and its modern name derives from its plan. Measuring approximately 60 x 30 metres overall and built of finely dressed masonry set on foundations of high grade concrete, it consisted of a central, oval courtyard around which, set concentrically, was a range divided into twelve wedge-shaped rooms and fronted by a colonnaded portico. These chambers were entered not by conventional doorways but by arched entrances 4 metres wide and nearly 6 metres high raised on massive stone piers. A little way into each room was a low wall which would have supported either a screen or balustrade.

The Elliptical Building was enclosed within a rectangular frame in order to reconcile its odd shape with the street grid of the fortress and was also provided with a range of outward-facing chambers along both of its shorter sides, each again fronted by a colonnaded portico. Access to the interior of the building was restricted to two long and narrow entrance passages, one set in the middle of each of these ranges.

At the centre of the courtyard lay a fountain-monument, undoubtedly intended to be accompanied by a pool. The lead water-pipe supplying the monument, found in 1969, bore a cast inscription recording its manufacture during the reign of Vespasian, when Gnaeus Iulius Agricola was Governor of Britain, and the consular dates enable its manufacture to be placed in the first half of AD 79. Thus, the Elliptical Building was an integral feature of the original fortress plan.

Following cessation of work on the Flavian building, perhaps a consequence of Agricola removing most of the legionary garrison ( legio II Adiutrix at this time ) for the advance into Scotland, its site lay largely derelict for the next 150 years, the elements of the unfinished structure gradually disappearing beneath a mound of rubbish.

With the comprehensive reconstruction of the Chester fortress instituted during the first half of the third century, the Elliptical Building project was revived. This time the building was actually completed, albeit with considerable modifications to the original design. As all traces of the original building had disappeared and as no attempt was made to trace the earlier foundations, this must mean that the original plans had been retrieved from the fortress archives where they had lain for 150 years!

With its unusual design, high quality construction, and the fact that it was one of the few fortress buildings to be built in stone at this period, the primary Elliptical Building was clearly something rather special. Apart from its plan, there are few clues as to its intended purpose because of its unfinished state. No precise parallels can be found, in either military or civil contexts, and so it can truly be called unique.

The lack, until quite recently, of a detailed published plan has hindered speculation as to its function although a number of suggestions - including a palace, a weapons-training school, a schola , or a market - have been proposed. However, none of these suggestions is really convincing. The form of the principal chambers endows the building with a monumental and commemorative, even quasi-religious character; an impression reinforced by the fact that the foundation of the courtyard fountain sealed a rock-cut trench which seems likely to have been the focus for a ritual ceremony associated with its inception.

Although temples were normally sited outside the defences one dedicated to the official deities of the Roman State, or to Roma et Divi Augusti, might have been permitted inside. It is even possible that the plan of the Elliptical Building was meant to be a symbolic representation of the geographic extent of the Empire, with its provinces grouped around the Mediterranean (the latter represented by the pool and accompanying fountain?), and/or the oval shape, as it was then perceived, of the entire inhabited world (Oikumene ). As an "Image of the World" (imago mundi orimago orbis terrarum) it would presumably have been the intention to adorn the building with statues, sculptures and pictorial representations of its regions and peoples.

Why should such a comparatively exotic building have been included in a legionary fortress on the fringes of the Empire at so early a date? The Elliptical Building should perhaps be viewed in conjunction with a number of other features of the legionary fortress at Chester which set it apart from contemporary establishments, not the least of which is the fact that it is 20% larger than the other early Flavian legionary fortresses at York and Caerleon. At the time Chester was founded, circa AD 76, its geographical and strategic position would have made it an ideal location for the headquarters of the provincial governor and the need to provide accommodation for the governor, his retinue of officials, and his personal bodyguard would explain both the unusually large size of the Chester fortress, the presence of a building whose architecture was more metropolitan and civil than provincial and military and which was but one of a group of unusual buildings occupying the centre of the fortress. Perhaps, therefore, the lead water-main found in the Elliptical Building and that previously recovered from the central area of the fortress (RIB II.3 2434.1-3) which bear cast inscriptions referring to Agricola ought to be taken as straightforward evidence of the intention to make Chester the headquarters of the provincial governor. The fragmentary slate-cut inscription found near to the Elliptical Building in the late 1960`s (Britannia II (1971), 290 No. 7), the only example of its class from Britain, might also be connected with the postulated unusual status of Deva .