The area under investigation is situated within a vast open area, south of the church of S. Stefano dei Cavalieri. The area is of particular interest with regard to urban development in medieval Pisa, as it was at the edge of the political heart of the city and the site of metalworking installations. In fact, the church of S. Sebastiano _de Fabbricis_ stood here, attested from 1074, and demolished to make way for the construction of S. Stefano dei Cavalieri (1565-9). Two trenches were excavated, sector 100, right by the church, and sector 700 south of the first. Between the 12th and 15th century the area was characterised by the presence of two rather simple buildings, separated by a dirt road 2.60 m wide, and destined for productive, service and residential purposes. Between the 12th-beginning of the 14th century the north building (sector 100) was used for metal working activities, firstly iron and later mainly bronze. Subsequently, in the 14th century, it became a storage facility. The structure had only one floor, no ceiling, and until the second half of the 14th century had low walls and a roof of shale slabs supported by a timber frame. The presence of low walls relates to metalworking, which produces abundant and noxious fumes and thus requires constant aeration, and a covered space not directly exposed to sunlight. With the subsequent changes in function and the transformation into a warehouse, the timber frame was demolished and the walls heightened, whilst the shale roof remained in place. The south building (sector 700), of which two stretches of parallel walls 3.20 m apart and the floor levels remain, was a residential structure. It comprised a ground floor which seemed to have been divided by a series of timber walls, and an upper floor of the _casa solariata_ type. The roof was also of shale slabs. Its collapse, caused by a fire, preserved some partially burnt straw interpreted as roofing insulation. Following the collapse of these buildings, during the first half of the 15th century, the area was abandoned. The north building was robbed in the third quarter of the 15th century, whilst the south building was robbed at the same time as the demolition of the church of S. Sebastiano and the subsequent construction of S. Stefano dei Cavalieri (1565-9). The area remained an open space the faint traces of which were attested by the late 17th century building site for the enlargement of the church and the creation of an area with trees.

Following the 2007 investigations four geognostic soundings were undertaken at the edge of the excavations which aimed to evaluate the area’s archaeological potential. Depths of ten metres (S1, S2, S3) and fifteen metres (S4) below ground level were reached. Starting at the lowest levels a series of alluvial deposits was recorded, datable, on the basis of the pottery fragments present, to the beginning of the 1st millennium B.C. From the Etruscan-orientalizing period onwards the area was settled and was characterised by a marshy environment, at the edge of an ancient riverbed identified in thermographic images of the Pisan substrate. In S1, S2 and S3 numerous fragments of wattle and daub, kernels, baked and partially vitrified clay and a small copper sheet were present, perhaps to be linked to the presence of production activities. This material was associated with pottery - bucchero _Kylikes_ and a small container for transporting wine (perhaps of oriental production) – which would seem to indicate a privileged economic context. S4 contained the most plant and wood remains which supports the hypothesis of the presence of an ancient riverbed, to whose banks S4 was the closest. Overlying this situation the core samples documented a layer of sand between 20 and 40 cm thick interpreted as flooding which occurred between the archaic and Hellenistic periods. Up until the Augustan period little residual material was noted. The transformation fits in well with the foundation of the _Colonia Opsequens Iulia Pisana_ between 41 and 27 B.C. The Roman occupation seemed to have lasted from the Augustan period until the 2nd century A.D. It was documented by a large quantity of material, mostly small abraded fragments, associated with fragments of panchina stone and _opus signinum_. The sediment typology, large quantity of faunal remains and charcoal, the size and fragmentation of the materials suggest the presence of an open area used for cultivations or as a rubbish dump. The excavation at Santa Apollonia revealed the presence of a building that remained in use during the 1st century and, probably, until the end of the 2nd century A.D., confirming the dating from the core samples. Between the Roman and early medieval phases the cores S1, S2, S4 showed a series of layers characterised by an abundance of shale slabs perhaps resulting from the roof collapse. What little material was present was mainly Roman, but the presence of such a large amount of shale suggests a late medieval date, as the use of this material became common in this period. Above these layers were strata characterised by a large amount of waste from iron working, datable to the early medieval by 9th century Forum Ware and attributable to the presence of an ironworks. During the middle centuries of the Middle Ages the more or less continuous presence of waste from iron working was interrupted in the levels dating to between the 11th and 12th century by the creation of new floors.