The purpose of this paper is the detailed study of one of the excavations that has marked the evolution of Fontbouïsse of MITRA III located in Garons (Gard, France) whilst focussing on the development and the disappearance of enclosures in the south of France. The site located near to a site known as Puech Ferrier, an unpublished enclosure of MITRA III excavated in 2011, was first excavated in 2012 within the framework of preventive archaeology. This exploration of a 5000 m ² surface revealed the southern part and the entrance of an installation delimited by at least two ditches which succeed one another, dating to a period between the 27th and 24th centuries BC that includes the development of the culture of Fontbouïsse, the Campaniforme (Bell Beaker) and the emergence of the early Bronze (BA2). A network of three concentric ditches, the innermost enclosure being the oldest, makes up the first enclosure, where an interruption in the ditches allows access to the site. A later much larger wider and deeper ditch cuts across the first enclosure. The paper focusses on the study of this ditch and its fill, which is the only enclosed site dating to the Late Neolithic in the south of France. Observed over nearly 90 m, this ditch delimits the southern part of the site. It contains fragments of mudbrick over a silty ashy layer the anthracological spectrum of which contains mainly by oak. Based on the results of stratigraphic and soil micromorphology, a phased filling of the ditch can be proposed. Micro-and macroscopic characterization of the earthen elements found in the ditch have specified the nature of the cob and wattle and daub and the demolished structure they came from. The findings reveal that the ditch remained open for a relatively short period of time, after which a cob structure, perhaps a wall, was installed, the base of which is preserved in a portion of the ditch. The ditch was then filled in by the destruction of another earthen and wood structure. This architecture could have been used to strengthen the monumental aspect of the enclosure, the hypothesis being that it copied a layout observed on other Fontbuxien settlements. A violent fire subsequently destroyed this ditch-wall enclosure and a possible adjoining building. Following on from this event, the ditch was re-dug before being filled in after the site is abandoned. The exact dating of the ditch and the destruction of the earthen wall remain imprecise. Some elements found in the lower ditch fill date to the first phase of the Fontbouïsse culture. They stylistically refer productions from the plain of Hérault and Gard. However, the destruction of the earthen architecture is dated by radiocarbon analysis and pottery found in the upper layers and the discovery of a sherd with international style decoration gives a later dating range of between 2450 and 2250 cal. BC. This enclosure and its destruction constitute a milestone in Fontbouïsse and Late Neolithic chronology. Its foundation and destruction occur within a short space of time. The events that occurred during the history of MITRA date the initial foundation and development of the concentric enclosures and the site''s total overhaul, which happened shortly before its abandon. The entrance identified at Mitra III, the new ditch with its earthen architecture that cut across the first enclosure around 2500 cal. BC questions our knowledge of the development and disappearance of enclosures at a pivotal period (Late Neolithic-Early Bronze Age) in southern France.