Roman imperial authorities built a city named Noviodunum on the site of a temple of the Celtic Diablintes, which became the capital of this people in the Augustan administrative reorganization.

In late antiquity the settlement lost its status as a capital when the Diablintes were absorbed into the Cenomani culture.

[2] Even though a simple bourg replaced the Roman city, the remarkably well-preserved ruins make Jublains an exceptional site.

Jublains has been inhabited since at least the La Tène culture in the Iron Age, although the archaeological record confirms that it was hardly urban at that time.

[4][3] The city named Noviodunum (Gaulish: "new fortress") was the most important Diablintes settlement and was mentioned by Ptolemy[5] and included in the Tabula Peutingeriana, where it was erroneously labelled Nu dionnum, on the same road as Araegenue.

[3] The temple was rebuilt in stone at some point after 65, and public monuments were erected, and contributed to the Romanisation of the local population.

The site was initially described as military, but in the 1970s, the work of René Rebuffat highlighted its role as a relay station linked to the cura annonae, a function enabled by Noviodunum's favorable road access.

[10] The settlement had declined sharply by the 4th century;[11] the coins and imported ceramics found at the site date no later than the reign of Constantine or Magnentius.

[9][10] Noviodunum was by then distant from the roads toward the Germanic limes,[12] and more importantly faced competition from growing cities like Le Mans.

[9] The location continued to be inhabited even though it was Vindunum, the capital of the Cénomans, (which became Le Mans) that was the metropolis and the seat of the Episcopal see.

[14] Other excavations in the area of La Tonnelle at the end of the 18th century unearthed important, long-known ruins,[17] which had since disappeared.

They were published in the papers of the principal protagonists: François-Jean Verger, Augustin Magdelaine and Henri Barbe[19] At the beginning of the 20th century local archeology suffered setbacks, as sites were looted for construction materials.

[20] Since the 1980s, and especially since the advent of the archeological service in 1988, Mayenne has carried out land management efforts to make the ancient city more visible.

[25] According to Jacques Naveau, "the main feature of this plan is the alignment of public buildings along a north-south axis, which seems central" over a length of 800 meters.

The city does not seem to have had sewers in the streets, apart from wastewater drains of the bathhouse,[27] nor an aqueduct except the one underground that fed the baths on the site of the current church.

[9] Workshops, including those of potters and glassmakers[24] and scattered dwellings give a total footprint for the Diablintian city of a hundred hectares.

The inscriptions discovered on the site were able to confirm this identification; one, on an altar with alleyways,[clarification needed] bore a dedication to Jupiter.

During his research, Henri Barbe discovered a coin bearing the portrait of Tiberius,[29] which makes it possible to envisage a construction of the whole after the reign of the latter.

[37] Established on a slope at the edge of town, today it faces a pastoral panorama of bocage, with the Coëvron hills in the background.

However, in the excavations of the castellum archaeologists found fragments believed to have come from the same decorative element, called "mask pillars".

[38] Archaeologists also found terracotta statuettes of Venus and a monolithic Iron Age stele, which still stands to the right of the orchestra.

[41] In the center, a massive rectangular praetorian tower of 22 × 23 meters[42] was built at the end of the 2nd century or the beginning of the 3rd.

[41] An earthen rampart preceded by a ditch ten meters wide, pierced to the south-east by a door,[42] surrounds the tower and testifies to the urgency of the security situation at the end of the 3rd century.

[48] This state of incompleteness is perhaps due to the loss of the strategic importance of the Diablintian city in favour of the Rhine border.

[10] The construction was long considered defensive in nature, but some historians believe it was used to store grain or more precious goods such as gold or tin.

[49]The thermal baths complete the monumental adornment of the city under the reign of Trajan[34] even if works were still taking place under the Severi.

New excavations to clarify the plan took place outside the building around the year 2000; materialized at the level of the forecourt of the main portal of the church.

If the pool basin was larger in its initial state,[31] the renovation with shale paving dates from the second half of the 2nd century.

[55] Coins bearing the portrait of Nero, from after AD 65, have fixed the date of the replacement by a stone edifice of the original Gaulish construction.

Research on the city has expanded since 1990, in conjunction with the real estate acquisitions and a rigorous excavation program.