Mausoleum of Centcelles
Constantí, Spain
The Roman villa of Centcelles is located in the municipality of Constantí, in Catalonia (Spain). It contains a masterpiece of Early Christian Art. In one of its rooms, which has been almost completely preserved, you can see the oldest known dome mosaic with a Christian theme in the Roman world, dated to the 4th century AD.
Archaeological site data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).