The Fossa Nera B complex is situated on the right bank of the river _Auser_. The river divided it from the Fossa Nera A farm which stood on the opposite bank. Excavations undertaken from 1999 onwards have brought to light the imposing foundations of a late Republican (200-175 B.C.) structure, of which sections of dry stone walling still survive. The blocks sometimes rested on a sort of foundation platform, constituted by cobbles and stone chippings, in other cases the blocks were lowered directly into the foundation trench where the soil was probably more compact. Neither were the walls built in a uniform manner: in some points there was a sort of _emplekton_ comprising two rows of blocks, the gap between them filled with earth. In other cases the blocks were juxtaposed and regular. The two different techniques appeared to belong to the same period. Many dividing walls, built using various construction techniques and from various periods, were also uncovered. The eastern perimeter wall, uncovered for its entire length, measured 120 feet and seemed to be linked to the module used in the first colonial settlement, as at _Luca_ the late Republican _insulae_ appear to be based on multiples of the _actus_. The internal division of the complex was well organised. It is possible that the northern part, with its square plan, was the residential area, whilst the southern zone was characterised by a series of rooms for production activities. A large quantity of pottery and metal was recovered from the northern sector, and the vertical stratigraphy revealed four occupation phases and sub-phases on the site. Originally, the summit of the rise on the right bank of the _Auser_ was occupied and defences created by the raising of a wooden structure: this was either a forerunner of a more solid and long lasting stone construction, or itself an actual fortification, as suggested by the substantial dimensions of the perimeter post holes. However, its size cannot be established. On the basis of the pottery recovered _in situ_ (fragments of early Graeco-italic _amphorae_ and black glaze ware), the wooden structure dates to between the end of the 3rd and the first quarter of the second century B.C. In the second phase, the wooden fortification was substituted by a stone, and polygonal perimeter walls were built. In this phase the complex was altered and restructured: the date of the change has yet to be established. In the Augustan period (phase III), the floor level was raised by a fill of earth, rich in finds, in which some storage vessels remained _in situ_ in the ground. This was sealed by a beaten floor surface. Around 50 A.D. (phase IV), the floor level was again raised and a new beaten floor surface created, of which only a few patches remain. The habitation was provided with an unusual brick-built _impluvium_, the horizontal parts of which were hidden from sight by an overlying stratum of yellowish soil. Around the middle of the 2nd century A.D. the habitation ceased to be used. The strategic position south of the _Auser_, the internal and external perimeter structures, the presence of buttresses along the perimeter walls, are elements which suggest that originally Fossa Nera B was an unusual type of fortification. It remains to be established whether this was a fortified farm of the Hellenistic type, with a dual productive and military role from its origins, or whether it was a military _castellum_ that was subsequently turned into a farm.