Where the Janus theory comes from
The theory has a paper trail, and it starts with a cathedral prebendary rather than a Roman text. Pablo de Céspedes held his cathedral post for over thirty years, from 1577 until his death in 1608[5], and his essay answered an antiquarian tradition about the building that Ambrosio de Morales had started in the last third of the 16th century[6].
Céspedes closed his argument by identifying Janus with Noah, which carried the temple all the way back to early Christianity[7]. A pagan shrine, a biblical patriarch and a Christian cathedral could then share one foundation story.
As a chain of reasoning it is tidy, and that is part of its appeal: two stones, one god, one patriarch, one cathedral. It is also a chain with a single weak link at the start. Everything depended on two milestones, and on what the inscriptions on them actually say. If the first link breaks, the Noah of the second step has nothing left to hold, however learned the literary sources that surround it.
What the milestones actually say
Two Roman milestones from the road now stand at the entrance of the Mezquita, and reference works on Roman Spain still describe the building as a reused temple[8]. Céspedes had made those stones the foundation of his case, reading them as naming a temple dedicated to Janus Augustus[9]. Both ideas trace back to the same reading of the same inscriptions.
Modern epigraphy dismantles it. Stylow, the epigraphist, called the Janus Augustus temple a phantom born of a misunderstanding of the milestone inscriptions[10]. Read correctly, they describe something else entirely. The temple was a phantom; the arch was real.
The slip is easy to follow. A reader already hunting for classical remains inside a cathedral, and handed a stone that names an Ianus Augustus, will look for a shrine nearby. A monumental arch standing on a highway suggests no such thing, so the error lived on in the reading and not in the stones themselves.
Why the theory lasted three centuries
Counted from the dedication mass held on 29 June 1236[13], the Mezquita had been a cathedral for almost four centuries by Céspedes's day, and its chapter was still praying in an unmistakably Islamic building. His essay landed during the last construction phase of the new cathedral nave, which was then being dressed in classical language[14], and the art historian Antonio Urquízar reads it as an attempt to de-Islamise the Mezquita[15].
Almost nobody pushed back. Pedro Díaz de Ribas was the only early modern writer to contradict Céspedes, pointing to the lack of serious historical argument in his reasoning[16]. In 1744 Tomás Fernández de Mesa went the other way and put a number on the myth: 2,384 years since the temple's foundation, of which only 347 had been Muslim[17]. On that reckoning the caliphs were a short interruption in a very old sacred site.
What the ground under the Mezquita does show
Where the theory predicts temple foundations, the excavators found a church. Félix Hernández Giménez dug inside the building between 1930 and 1936[20], and the cathedral's own history says his aim was to learn more about the Visigothic Basilica of San Vicente[21]. He wrote no excavation report, the compulsory bureaucratic ones have not yet been found, and the photographic archive survives in the Museo Arqueológico Provincial[22].
Three points mark where the evidence stands now:
- The basement room of the basilica carries a brick-and-masonry inscription, EX OFF[ICINA] LEONTI, that names the workshop and dates the construction to the 6th century[23].
- The 2021 dig in the Patio de los Naranjos, continuing Hernández's 1934 trench, points to a large 5th-century episcopal complex that was the city's nerve centre before the caliphate[3].
- As of the April 2021 reporting, that dig had not reached Roman levels, and the excavators say that of earlier periods "we know nothing"[24].
Nothing in the documented finds is a temple of Janus, and the Roman layers beneath remain unreached in the Patio, so the question is open at depth but empty of support in everything recorded so far. The official Mezquita site describes the 6th-century remains as the Basilica of San Vicente[4], while the 2021 dig reporting describes a 5th-century episcopal complex in the courtyard[3]; the pre-Islamic archaeology of the site tells the longer story.
Explore nearby · Monument
Mezquita-Catedral de Córdoba
856 columns, 1,300 years of Islamic and Christian history. UNESCO monument in Córdoba, Andalusia. Red-and-white arches, Byzantine mosaics, a Renaissance nave.
What a visitor can actually see today
Inside the Mezquita-Catedral the pre-Islamic layer sits in the basement, where the archaeological remains of the Visigothic Basilica of San Vicente are kept[4]. The mosaics from a room of the original basilica continue the Roman and Paleo-Christian tradition across three decorative areas[25], and some of the pieces recovered in the excavations are exhibited in the monument today[26]. It is a church floor, not a shrine to Janus, and that is the honest answer to the question that brings most people here.
The cathedral's own pages on its history and on the basilica tell the San Vicente story and never mention Janus[4]. The Roman and Visigothic material in the prayer hall is reused stone, most visibly in its mismatched columns, not the footprint of a temple.
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If you want a Roman temple, the one that has actually been excavated in Córdoba is a separate building, the Roman temple, which stands at the corner of Calle Claudio Marcelo and Calle Capitulares, next to City Hall[27]. It needs no myth to be worth the walk. The Mezquita's real pre-Islamic story is the Christian one in its basement.
Deep dive · Article
Abd al-Rahman III: The Morning Córdoba Became a Caliphate
Abd al-Rahman III was the first Caliph of Córdoba, declared on January 16, 929, ruling Córdoba for 49 years and starting work on Medina Azahara in 936 CE.
So when a plaque, a guide or a website tells you the building is a reused Roman temple, ask which excavation it means. The honest answer today is a late antique Christian sequence under the building, plus Roman stone that was carried in and reused, and none of it is shaped like a Janus shrine.