[1] Peaking at 1,077 meters in altitude, the col was, until the 18th century, the primary communication route between the expansive Limagne plain to the east, the Dore mountains to the southwest, and the Combrailles to the northwest.

[5][6] The climate is marked by some extreme weather conditions, including severe winters, violent storms during the summer months, and a high level of precipitation, in the form of rain and fog.

[4] The forest covering the col consists of spruces and beeches,[6] planted between the late 19th and early 20th centuries as part of a large-scale reforestation program for the Chaîne des Puys.

[7][8] While this wooded relief occasionally presented challenges to research,[9][10] it also served to protect the site by mitigating the erosion of the slopes,[11] whose sediments have long covered the remains.

[12] The geology of the Col de Ceyssat is defined by trachytic eruptive products from the Kilian explosion crater, which extend to the col.[13] Human occupation during antiquity resulted in the construction of terraces[14] that significantly altered the organization of the terrain until the site's abandonment and subsequent collapse.

[16] Its capital, Augustonemetum, was constructed at the end of the first century BC at the site of the future city of Clermont-Ferrand,[17] situated approximately 10 kilometers east of the secondary settlement of the Col de Ceyssat.

[19] In the commune of Orcines, to the east, at a place called La Baraque, approximately five kilometers from the col, the existence of another opulent rural residence, also interpreted as a villa, was revealed by the discovery of mosaic tesserae in the late nineteenth century.

[6][51] At the turn of the 2000s, research on the Col de Ceyssat experienced a resurgence, driven by a convergence of academic inquiry, rescue archaeology initiatives, and the repercussions of the 1999 storm [fr] on the surrounding forest landscape.

[60][61] The initial surveys, spearheaded by Frédéric Trément [fr], were conducted in April of the same year to accurately delineate the characteristics of the structures excavated between the late 1970s and 1980s in the northern sector of the Col de Ceyssat.

[9] Between June and July 2003, a long transect was conducted west of the Col de Ceyssat, at the level of the Puy Besace, at the site of the Roman road and an ancient building previously discovered.

[66] The current state of knowledge of the Col de Ceyssat is primarily due to the operations led by Frédéric Trément, which have allowed for the archaeological documentation of various sectors of the settlement.

These included a diagnostic study conducted at the col's parking area in November 2003,[69] the installation of a drinking water supply network to the summit of the Puy de Dôme in March-April 2012,[70] and finally the redevelopment of the Auberge des Muletiers in April 2019.

[68][73] Meanwhile, a geophysical ground-penetrating radar survey has enabled the creation of 18 profiles in the western part of the lower quarter,[74][75] in preparation for new research projects at the Col de Ceyssat.

[103] The walls and buildings identified during soundings and surveys[70] often provide evidence of meticulously constructed structures in reticulated masonry[62] utilizing volcanic ejecta from the surrounding mountains, including trachyte, basalt, and scoria.

[104] Among the network of constructions,[14] one building has notably yielded marble, a fragment of sculpture in domite,[104] and a mother goddess in white clay from the Allier,[105] while others have produced hypocaust pipes and painted plaster,[104] and even mosaic tesserae.

[114] A total of 72 pieces of graffiti, either representing abbreviated formulas or initials, were identified on ceramics in Sector 1, predominantly on fire pots, including jugs and kettles.

Alternatively, the existence of a bypass before entering the hollow way and ascending to the pass, with all that it implies in terms of personnel and structures for accommodating men and mounts, may have been a significant influence.

[135] However, the boundaries of the funerary zone remain unknown due to its location on the eastern slope of Puy des Grosmanaux [fr], where the steep incline presents a significant challenge for pedestrian surveys.

[136] The available literature reports some ancient discoveries, including a stele[note 7] depicting a female figure in a small niche measuring 45 × 30 × 25 cm[137] and weighing 19 kg,[138] which was unearthed during the winter of 1886–1887.

[15] While the possibility of a water supply originating from sources situated a few kilometers away has been contemplated, the discovery of a considerable number of jugs and kettles during the surveys of the cult area indicates that rainwater was purified in these containers before any domestic or cult-related usage.

"[158] At the beginning of the following century, Auguste Audollent offered a more precise indication:[4] It is not only at the summit of the puy but also on its slopes (Redon, Col de Ceyssat), at its base (La Tourette d'Enval), that important archaeological remains have been found.

[56] It was only as a result of the storm of 1999 [fr] and the implementation of preemptive excavation operations that the possibility of "considering the hypothesis of a secondary settlement linked to the temple of Mercury" could be explored.

[50] Frédéric Trément advanced the hypothesis that the settlement at Col de Ceyssat should be identified with Ubrilium, whose distance from Augustonemetum corresponds exactly to what is indicated on the Peutinger Table (equivalent to 13 km).

This stele was linked to the sanctuary of La Tourette: A votive inscription suggests that, aside from the monumental temple erected at the summit of Puy de Dôme, there might have been a more or less significant sacellum near the southern base of this mountain and at the entrance to the Ceyssat pass.

Pierre-Pardoux Mathieu [fr], who was the first to establish a link between the remains at the pass and the proximity to the Temple of Mercury,[158] wrote: It was at the foot of the Wasson,[note 8] a thriving town under the influence of Roman civilization, which must have been, during the winters, the residence of ministers attached to the sanctuary.

[176]In a subsequent publication, Auguste Audollent articulated a more nuanced perspective on the constructions at the Ceyssat pass, suggesting that they were intended to provide accommodation for travelers and pilgrims.

He also offered a detailed analysis of the sanctuary of La Tourette:[177] Those who were afraid of the ascent, due to their age or frail health, could, it seems, satisfy their piety without exposing themselves to such fatigue.

At the Ceyssat pass and on the western flank of the Puy, at a place called 'Redon,' where the automobile road intersects the path with its sixteen bends, archaeological remains have been unearthed.

[180] Florian Baret's doctoral research on secondary agglomerations in the Massif Central permitted the repositioning of the Ceyssat pass settlement in a broader regional context.

[151] Additionally, the peripheral placement of a cultic area is a notable feature, as evidenced by the archaeological site of the Croix de la Pierre in Charbonnier-les-Mines [fr].