The stratigraphic reading of the walls had documented the existence of five phases in the Santalla de Bóveda Monument. The samples taken in 2007 and 2020 were collected considering this sequence with the aim of dating and characterising the construction materials, specifically the mortars. As can be seen, both in terms of characterisation and dating, the mortars are divided into four large groups.
In Phase I (Fig. 6), the mortars collected roughly oscillate between the year 28 and 602, with the second half of the 4th century being the time when they coincide with each other. However, there is a group of mortars dated by 14C that fall outside this range, one (BOV20MU001_A_P) dating from 1175-1324 AD, another (BOV20MU002_B) from 1607-1506 BC and two others (BOV20MU003_A_P and BOV20MU003_B_P) from 760-363 BC and 43-209 BC respectively. However, this disparity does not occur between the dates obtained by OSL. As for the bricks, the pattern is repeated, ranging from 55 to 602 AD. Thus, considering the coherence and coinciding range of the mortars dated by OSL, the phase corresponding to the construction of the aula was placed in the second half of the 4th century.
There is a series of mortars and bricks collected in the vault of the apse and in the horseshoe arch of the entrance, whose interval could be placed in both Phase I and II, as they present very large margins of error. In the case of the apse vault, the mortar corresponds to 344-920 AD and the brick 364-894 AD, both of which coincide quite closely with each other. Our assessment is inclined to place them in Phase I, considering the results of the reading of the walls, which indicate that the vault would have been made with the rest of the aula, as no cuts can be seen in it.
In the case of the aula entrance door, the mortar dates from 248-557 AD and the brick from 63 BC-597 AD. The reading of paraments placed this doorway as part of a Phase II alteration. In part, the most recent dating results lead us to a time immediately prior to the construction of the paintings, but it could also fall within Phase I, so we believe that either hypothesis would be feasible. In fact, if we look at one of the dates of the mortar used to prepare the paintings, it is very similar to these (346-526 AD). We thus leave both hypotheses open in this case.
The mortars collected from elements of Phase II (Fig. 6) were taken, on the one hand, from the remains of the central vault conserved in the Provincial Museum of Lugo (Spain), obtaining dates of 607-774 AD (MUSEB-001_P) and 434-603 AD (MUSEB-002_P), coinciding in the interval 603-607. On the other hand, the mortar used to prepare the paintings preserved in situ, dates ranging from 346 to 680 AD. In this case, they all coincide with the beginning of the 7th century, although one point must be made: in Phase II, all the mortars have been dated by 14C except for one BOV20MU008, which is slightly older and coincides with the dating of the horseshoe arch of the doorway to the aula, which would date to the end of the 6th century. In other buildings it has been found that the carbonation of the mortars is not immediate, but occurs some years after the time of laying (Lindroos et al. 2020; Daugbjerg et al. 2021), so it could even be hypothesised that this reform corresponds to the end of the 6th and beginning of the 7th century.
Understanding these data in context requires further research, an intensive analysis of the environment of the Santalla de Bóveda Monument, and of the place where the building is located. But three aspects should be highlighted that open up new hypotheses on which to continue working. The first building is framed in a historical context in which in Gallaecia there was a ruralisation of the territory with the increase of villae and other types of rural settlements and their functions, especially in the surroundings of the cities. The 4th century sees the greatest development of this type of settlement (Carlsson-Brandt 2021: 690), a phenomenon also closely associated with the occupation of the vicinity of the roads that articulate the territory; in fact, the Santalla de Bóveda Monument is located in a central place between the XIX and XX Roman Vias, in a flat area and close to several hillforts (Gómez 2005: 191), a fairly common proximity in relation to the villae (Carlsson-Brandt 2021: 688-689). From our point of view, the Santalla de Bóveda Monument would most probably be part of a type of Roman rural settlement that, at least, would have a phase in the second half of the 4th century, but determining its typology without a detailed knowledge of the whole is adventurous. See the current case of the Roman site of Proendos (Sober, Lugo), whose geomagnetic prospecting has identified an important complex which is currently being excavated (Alonso et al. 2021) and which yields contexts from the 1st to the 6th-7th century AD. In the case of the Santalla de Bóveda Monument, there are few interventions that have been carried out in the area that allow us to advance this hypothesis. The excavations carried out by Gimeno (1989) point to the existence of Roman materials, most of which were dated between the 3rd and 5th centuries (Motenegro 2016: 284), coinciding with the dating of the first phase of the building. It should be noted that in the area around the Santalla de Bóveda Monument there are other settlements whose materials are also linked to Late Roman dates, such as the capital of Santa Cruz da Retorta Church from the 4th - 5th centuries (Gómez 2005: 193). Therefore, in view of the confirmation of the initial phase of the Santalla de Bóveda Monument in the second half of the 4th century, it would be necessary to review from this perspective these nearby contexts which point, as several authors point out, to a high degree of organisation and development of the rural settlement during this period (Tejerizo 2020: 165) which in the Santalla de Bóveda Monument has a continuity in the following centuries, if one considers the dating of the reform of the aula and the paintings of the vault, or the construction of the upper floor.
Focusing on the paintings, the samples collection was limited to the mortars of the preparatory layers of the painting without affecting them. In spite of this we count on the stratigraphic analysis made by Cabrera (1992) of four samples of painting. He emphasises the polishing of intonachi and the superposition of painting layers (Blanco-Rotea et al. 2009: 186-187). The identified pigments are: cinnabar, green earth, Egyptian blue, bone black, lime white and also verdaccio which he identifies with the description that Cennino Cennini gives for it.
Recent studies about the Egyptian blue, the use of which many authors claim was abandoned in the Roman age, demonstrate that it was still being used years later. Thanks to new technologies, its use has been confirmed even in the paintings of the Cinquecento. As for the verdaccio we have not found references to it before Cennini, although it is possible that a similar technique for the flesh colour was used in the Byzantine and Romanesque wall paintings.
These researches allow us to confirm that the absolute dates obtained in this study are not contradictory to the use of the pigments identified by Cabrera.
The dating of the paintings to the 7th century, far from being a problem, reinforces the initial hypothesis of the survival of Roman structural techniques, both because of their wide circulation over an enormous territory and because of their efficiency, which have proved to be of great quality and durability.
Thus, the permanence of the techniques, materials and pigments used in the paintings, while leading some authors to consider them Roman, others argued that the pictorial technique used in the Santalla de Bóveda Monument remained almost intact until the first centuries of the Middle Ages (Murat 2021: 17-19, 27), it occurs here with the technical realisation, the master lines and the colours palette (Benavides and Blanco-Rotea 2008: 68-72; Blanco-Rotea et al. 2009: 184-187).
An exact parallel with the paintings of the Santalla de Bóveda Monument is yet to be found, although there existed numerous partial parallels. Also, it is true that there are not paintings of the 7th AD century so well preserved apparently without restorer interventions and not even hidden by later plasters. Maybe because of the unusual conservation in painting it is more frequent to find parallels in mosaic of the same age, so much for the greater resistance of the materials and for the conservation of pavements with hardly any walls around them.
The decoration of the lost central part of the vault is documented in such a long period that it is possible to find parallels from the 2nd century BC, as Polybius house in Pompeii (Croisille, 2005: 74) to the Royal Palace of Caserta from the 18th century AD; although/even though the nearest are in the Asturian Pre-Romanesque (Arias Páramo, 1999) (Fig. 7). The vases with branches and flowers that we can see in the intrados have parallels in the Byzantine world and once more in the Asturian Pre-Romanesque (Arias Páramo, 1999: 77).
Birds, grapes, rosaceae and lozenges also appear during a long time in buildings whose functions are different and in territories very far apart.
Although in wall paintings we can rarely see them, the graticules made by successions of motives are frequents in the Roman world and also in much later moments as it is the case of the apodyterium of Qusayr’ Amra built in the 8th century AD (Almagro et al., 1975; Vibert-Guigue, 2004: 210-213; Manzano, 2007: 339) or the Sala delle Oche in the Palace of Bonifacio VIII (Anagni, Italy) (1294-1303) (Fig. 8).
In mosaics (Fig. 9), the model which presents more similarities with the Santalla de Bóveda Monument is the one of the vault hall of the chapel of Sant'Andrea in the Archiepiscopal Palace of Ravenna, from the era of the bishop Pietro II (494-519). The floral lozenges are populated with various species of birds.
With variations on the same theme we can find several mosaic floors, in some cases like in Apostles Church of Madaba (Jordan) another mosaic is preserved with the same geometric pattern of the lost vault (Fig. 9). Also in Madaba, and from the same century, we find this scheme in the Church of al-Khadir or the Church of the Martyrs, representing birds, flowers, grapes and other fruits. All of that leads to show the chronological, geographical and functional dispersion of the pattern of the aula vault.
Regarding the remains of the vault preserved on the upper floor, we had already raised on other occasions (Blanco-Rotea et al. 2009) the complexity of linking them to phase I or II, as the relationship between them was severed in the reform carried out by Gallego and Portela in 1985-1993. However, the difference in the construction technique used between the vaults of the aula and the upper floor led us to assume that these were different phases, as corroborated by the results of the dating, which lead us to firmly establish the existence of a third phase in which a room was built above the aula. However, in this case the dating is also somewhat disparate. There are two OSL mortar dates that we consider to be in error, AUE110 gives a date of 3267-2091 BC and AUE017 of 417-127 BC. The remaining ones range between 764 and 1475 AD, with the 10th-12th centuries being the coinciding dates. On the other hand, in the case of the bricks used in this vault, the dates range between 336 and 919 years, coinciding in the interval 648-739 AD, which leads us to wonder if they are not reused bricks from another building or from the lower structure.
We also link to this time a series of replacement mortars documented in the vault of the aula over earlier mortars and structures, also dating from around the 11th-12th centuries.
The Baroque phase, which should perhaps be associated with the time when the current Parish Church was built in 1750 and a ceiling was placed over the remains of the aula now filled with rubble from the upper floor. It corresponds to a mortar dated 1646-1799 AD.
 ‘burnt sienna, bone black, lime white and cinnabar’ (Cabrera1992: 38).
 ‘In the wall paintings of the church of San Saba (Rome), dating to the first half of the 8th century AD, Egyptian blue and lapis lazuli have been detected mixed together within the same pictorial layer’ (Gaetani et al. 2004: 13). ‘Egyptian blue has been identified positively in a Roman medieval fresco of the lower church of San Clemente’ (Lazzarini 1982: 84).
 ‘Egyptian blue was optically identified in a single thin section from a painting by Giovanni Battista Benvenuto from 1524, a period from which Egyptian blue is normally considered not to exist’ (Bredal-Jørgensen et al. 2011:1438).
 Cennino d’Andrea Cennini (c.1370-1440), a painter who describes the techniques of the master Giotto in The Book of The Art. The verdaccio’s description is very accurate in chapter LXVII, whereas it is quite simplified in chapter LXXXV.
 Dyonisius de Fourna (1670-1745), in his treatise Erminia picturii bizantine describes: ‘The flesh-colours are made with green earth, (...) dark ochre, (...) lime white (...) and black. Grind them well and use as base colour’ (Villarquide 2015:117).
 Eraclio says in De coloribus et artibus romanorum: ‘For the flesh-colours is sometimes used, mostly in Italy, a layer of verdaccio as in Byzantium, in which case the work is made basically from dark to light’ (Villarquide 2015:143).
In Ravena, in Gala Placidia mausoleum and Neonian Baptistery, both from 5th century AD and the Albenga baptistery, 5th-6th AD, all of them made in mosaic.
Pompeii (Croisille 2005:92), Domus Aurea (
S Segala, Sciortino,1999: 80), Villa di Arianna (Guinouves 1987:8-9; Formoso 2006: 87), villa di Popea in Oplontis or Villa di Minori in the Amalfitan coast (Laken 1998: 297 and 395). In this these two last cases, the succession of motives that made the lozenges are interlaced just as in Santalla; Abad Casal (1979: 920; 1982: 368) makes an interesting reflection of on? this ‘knot’.
Although much later than Saint Eulalia, this painting has in common with it the interlacing of the losanges, a large variety of birds - although only the geese give the room its name - and the hypothesis that the paintings were inspired by a treatise on birds (De arte venandi cum avibus in this case and the Dioscorides of Vienna in the case of Saint Eulalia).
In this case it is pergolato (arbour: mosaic and tempera painting). https://www.ravennamosaici.it/cappella-di-santandrea-e-museo-arcivescovile/
A mosaic inscription (later destroyed) indicated the name of the church and 578 as the year of the completion. https://universes.art/es/art-destinations/jordania/madaba/church-of-the-apostles (last search 28/11/2021).
 https://eldiwan2010.blogspot.com/2018/07/jordania-madaba-la-ciudad-de-los.html (January 2022 consultation).