1° In Limousin, our knowledge of ancient monumental funeral architecture has been given a new impetus for research during the past fifteen years thanks to the inventory of large-stone blocks reused in civil and religious constructions or even in later funeral arrangements. 2° It is from this standpoint that the Châteauponsac site has been included where, in an urban landscape, a large concentration of examples of ancient architecture are conserved. Among the major facilities preserving in their elevations a large number of these re-used stones is included the ancient Saint-Thyrse abbey church and the Porte Peyrine , which unlike the neighbouring religious building, has so far been the subject of no specific study. 3° The Châteauponsac site is in a privileged topographical position, since human occupation is concentrated in an interfluve zone between two valleys, that of the Semme to the north and that of the Gartempe to the south. These natural conditions, with the relatively steep slopes and the sharpe curve of the embanked meander of the Gartempe, constitute a place for a permanent, easily defensible establishment. Although, until now, known for its three medieval ecclesial poles, a human occupation from Antiquity has long been recognized. In the Merovingian period, the existence of two trientes constitute the first mention relating to Châteauponsac. However, the question of the precise location of the castrum Potentiacum was still posed, which led to consider several sectors of the city in relation to the topography, written sources and available archaeological witnesses. 4° Textual sources, essentially modern, provide only a fragmentary vision of a Late Middle Ages fortification. Nevertheless, several indications are provided by the ditches, towers and the names of the entrances to the city. Amongst the four main restored entry points the Porte Peyrine is absent. Although local scholarship traditionally associates it with the fortification work carried out between 1420 and 1454, its period of construction has always remained uncertain. This is why it appeared timely to initiate a first study taking into account the archaeological potential and the marginal place occupied by this monumental gate in the urban fabric. 5° Except for modern transformations, in particular the addition of a high hall covered with a gable roof, the sustaining walls in the western span and the semicircular arch in the eastern span, the Porte Peyrine conserves all of its initial volume.This massive construction, reinforced in the northwest and southwest by thick masonry, has a relatively simple plan, barlong with a floor area of almost 15 m2.This space is subdivided into two unequal parts lengthwise - 3 m for the eastern corridor versus 2 m for the western one -, separated by jambs 0.60 m high and 0.50 m wide. To the detriment of the eastern access, where only the two southern sidewall/jamb foundations are visible, the frame of the intermediate door is complete with its jambs marked by a chamfered jutting lower base, corbelled imposts and monolithic lintel. These two entries were initially closed by a double door attested by the circular traces left by the rotation axes. The fortified passage initially had a floor “built” of large flat stones, located 0.30 m below the current circulation level. This monumental pavement is intersected by two hollows with divergent orientations, probably both sepulchral as evidenced by the burial in a coffin of perishable material - oriented south-north -, deposited in a pit cut in the rock and delimited laterally by small “low walls”. The tomb was radiocarbon dated to between 779 and 969 A.D. which provides a terminus post quem for the construction of the door 6° The different archaeological approaches have made it possible to demonstrate that this monumental element is far from being isolated, since several segments of the curtain wall have been identified in the elevations of the adjoining civil structure, of which almost 25 m have been conserved. The sections studied allow reconstitution of an enclosure at least 2.60 m wide and 3 m high equivalent to seven courses of large stone blocks. There is a visible difference between the north and south curtain walls. On the southern side, the facings are characterized by a specific implementation: the foundations consist of four jutting foundations to the east of thin elongated blocks, while in elevation there is an alternation of rows of large blocks and rows of significantly smaller ones. On the northern side, the builders tried to rationalize foundation heights. Regarding blocking masonry (north and south), it is made of piled-up rough local stones of various sizes and shapes. It is undoubtedly economic and technical reasons, more than aesthetic, which explain this construction. The majority of the upper level blocks have broken angles - deterioration linked either to a brutal dismantling of ancient buildings, or to the removal of the metal ties at a later period –also many of them bore traces of the anchoring systems used to lift, assemble and clamp, unlike the lower rows.Although these different indices reflect ancient construction processes, it is difficult to determine whether these were specifically designed for the erection of the fortification. If this is not the case, it suggests an immediate re-use of these elements and why not a deliberate destruction of the original buildings. The use and assembly of this type of stone element are found on other sites such as Périgueux, Saintes or even Bordeaux, where the vestiges of the enclosures have been dated to the Late Roman Empire. 7° This combination of archaeological studies has made it possible to discern in the urban landscape of Châteauponsac a unique fortified structure, whose chronology, traditionally dated to the beginning of the 15th century, was revised to be earlier,and at the earliest Late Antiquity, at the latest the High Middle Ages before the 7th century, if one accepts the numismatic references Potincacocas (tro) or Potenciaco c. Its abandonment phase, which is not better understood, is perhaps linked to the coal seams of the seventh and eighth centuries identified in the Saint-Thyrse church. A profound reorganization of the urban space seems nevertheless to have taken place during the Carolingian period, with the probable enlargement of the funeray space up to the Porte Peyrine. At the beginning of the eighteenth century, the fortification was incorporated into the new civil building . 8° A true unicum in Limousin, since the Limoges ancient castrum wall is known only through a later written source, this monumental group is part of a phenomenon, now well identified, that of the re-use of ancient materials in the of mausoleum type funerary buildings, as attested by the epigraphic sources. However, the question of its function remains without it being possible to privilege certain hypotheses (vicus protected by a fortification, presence of a staging post monitoring the crossing of the Gartempe, a military fort located near an important crossroads built from Late Antiquity and transformed over the following centuries into a place of economic power,…?). 9° Despite a large number of uncertainties on its layout, its organs (towers, access) and use the first results contribute to increase our understanding of the genesis of Châteauponsac and its morphological evolution, and in particular reconsideration of the initial nucleus around the church of Saint-Martin. This study also makes it possible to enrich the particularly sparse corpus of fortified sites of Late Antiquity or the High Middle Ages in South-West France.