Yes / This paper summarizes the results of a recent geophysical investigation carried out at Porolissum, which is considered to be one of the most significant Roman sites in Romania. The geophysical survey was carried out within the latus dextrum of the fort, which is the same location that had been the subject of earlier geophysical surveys as well as older archaeological excavations (1970s) that had uncovered a multiroom building. A cesium vapor total field magnetometer and a multi-electrode resistivity meter for a dense Electrical Resistivity Tomography (ERT) survey were used. Eighty parallel ERT profiles in combination with the emerging total field magnetic data and an antecedent magnetic survey allowed us to complete a more precise interpretation regarding the building that once existed on the left side of Porolissum’s Principia (the commander’s house). In contrast to the magnetic survey, which only reveals a part of the building’s architecture, the ERT survey provides a comprehensive view of the structure’s layout. More than 20 rooms could be positively identified, and the existence of further rooms might be deduced from the data. The ERT scan revealed the existence of the building’s northern external wall as well, which is not reflected on the magnetic map. Because some parts of the building are not visible on the magnetic map, we can assume that the building was constructed with at least two types of rocks (magmatic and sedimentary). In addition to the archaeological interpretation of the geophysical anomalies, a number of discussions concerning the connection between our survey and the geology of the area were held. The complementarity of the magnetic and resistivity results prompted us to conceive a preliminary 3D reconstruction of the building. Even if the building function is unknown in the absence of reliable archaeological data, it could have been a storage building, a second praetorium, a valetudinarium (hospital), or an armamentarium (weapons storage building). The illustrative reconstruction was completed taking into consideration that the building was a Roman military hospital, which, based on the available data, may be considered a credible assumption.