The Basilica of Saint-Pierre-Aux-Nonnains is one of the oldest Christian churches in the world still standing. Erected sometime in the 4th century AD, it was originally part of a Roman-era spa when Divodurum, the former name of Metz, was a major military and trade center along the Germanic frontier. Specifically it was used as a pagan gymnasium when Christianity in Western Europe was still in its infancy. It was one of the few buildings in the city to remain standing after the Huns passed through in 451 AD.
Metz was an important cradle of Frankish civilization, with both Merovingians and Carolingians tracing their ancestry to the place. After the conversion of Clovis I to Catholicism, Metz became a Christian stronghold. During the 7th century, the old Roman gymnasium was converted to use as a Benedictine church. During the reign of Charlemagne, Metz was almost chosen as the capital city of the newly founded Holy Roman Empire, an honor which was instead bestowed on nearby Aachen. Neverthless Charlemagne was apparently fond of the old church, and two of his sons were buried in what would later be designated the Basilica of Saint-Pierre-Aux-Nonnains.
Amazingly, the original Roman structure remained essentially intact throughout the Middle Ages. Apparently by the 16th century the old edifice was showing its age, and the Church moved out. It then spent over 400 years in service as a warehouse: a perfectly intact thousand-year-old building, one of the best preserved Roman constructions in the world, was then used for storage. Thankfully, its historical importance was recognized in the 1970s and the basilica was restored. It is now used primarily as a concert hall, a fitting tribute to its medieval musical heritage.
The interior is much less Roman in appearance than the exterior, as the whole place was renovated in the 10th century, and again in the 20th century. Although still designated as a Basilica by the Roman Catholic Church, the building’s use nowadays is for musical functions and exhibitions. It is certainly an ideal place to see Gregorian Chant music performed.
References:The ancient Argos Theater was built in 320 BC. and is located in Argos, Greece against Larissa Hill. Nearby from this site is Agora, Roman Odeon, and the Baths of Argos. The theater is one of the largest architectural developments in Greece and was renovated in ca 120 AD.
The Hellenistic theater at Argos is cut into the hillside of the Larisa, with 90 steps up a steep incline, forming a narrow rectilinear cavea. Among the largest theaters in Greece, it held about 20,000 spectators and is divided by two landings into three horizontal sections. Staircases further divide the cavea into four cunei, corresponding to the tribes of Argos A high wall was erected to prevent unauthorized access into the theatron and may have helped the acoustics, but it is said the sound quality is still very good today.
Around 120 CE, both theaters were renovated in the Roman style.