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:Duino Castle was built by the Wallsee family in 1389 on the cliffs overlooking the Gulf of Trieste. It replaced an older castle from the 11th century. Over time, the Wallsee family disappeared and the castle, after having been used as a prison, became the residence of the Luogar and Hofer.
At the end of the 19th century it became the property of Prince Alexander von Thurn und Taxis from the Czech branch of the House of Thurn and Taxis. It remains with the family to this day with his great-grandson Prince Carlo Alessandro della Torre e Tasso, Duke of Castel Duino the current owner. The castle has been opened to the public as a museum and park.