Preparations for the war with the Dacians presumably in the very end of the 1st century AD brought entirely new investment in the form of an army hospital, one of the biggest known valetudinaria from the Roman period. The building was erected in place of the dismantled baths. It remained in operation until the first half of the 3rd century, when it was purposefully abandoned. The plan of the building is surprisingly simple but functional. It measured 81.90 x 72.90 m on the outside and contained a large inner courtyard lined with shaded porticoes (42.23 x 32.60 m ). Each wing running around this courtyard consisted of a circuit corridor down the center and two series of rooms on either side. The roof was consequently basilical in construction, the center part above the corridor being raised above the level of the rooms and furnished with big clerestory windows in order to light up the interior in daytime. Skylights existed in the corner rooms. The main entrance to the valetudinarium was from the via praetoria which was 6 m wide at this point. Lining the façade on this street was a wide outer portico. The main entrance was a monumental doorway flanked by engaged columns, closed with an iron-studded double-winged wooden door. The door opened into a corridor 5.20 m wide and gave straight into a courtyard. The hospital rooms were arranged in characteristic threes: two big rooms joined by an anteroom leading from the corridor. The vestibules were dark but the rooms had two big windows each. Window bays, at least 1 m wide, can still be seen in one of the rooms. The inner walls were plastered and painted red. The floors were made of layers of fine sand. The vestibules had furniture in the form of shelves for storing whatever was needed: plates, bowls, jugs, mortaria, lamps, glass vessels and amphora . Also caskets containing medicine, surgical instruments and cosmetic utensils. Candelabras and vessels stood inside the rooms. Each room could hold from four to six patients, which puts the total capacity of the hospital at about 300 legionaries. Some rooms were used as magazines of amphorae and tableware. There is also a latrine. The latrine channels contained many broken or unnecessary objects that had been thrown away as rubbish by their owners.
The army hospital was a unique discovery, mainly because it is one of the earliest stone hospitals and one of the biggest — almost 6000 m 2 in area. It is also among the best preserved buildings of its kind from the territory of the Roman Empire . A small temple to Asclepius stood in the center of the courtyard. The chapel, measuring 2.46 x 2.60 m , was raised on a low podium with steps leading up to the interior of the sacellum . A low wooden screen between the two columns in the front portico guarded the entrance. Altars, statue bases and votive slabs to other deities, such as Juno and the Capitoline Triad, were erected in the unpaved courtyard around the temple. A passage paved with roof tiles ran from the entrance to the temple, facilitating communication and emphasizing the E-W axis of the architectural complex.