Baptistry of Neon (church building) built
401 CE.
Shown on the map at 44.416°, 12.197°.
The Baptistery of Neon (Italian: Battistero Neoniano) is a Roman religious building in Ravenna, northeastern Italy. The most ancient monument remaining in the city, it was partly erected on the site of a Roman bath. It is also called the Orthodox Baptistery to distinguish it from the Arian Baptistery constructed on behest of Ostrogothic King Theodoric some 50 years later.
Text from the Wikipedia article Baptistery of Neon, licensed CC BY-SA 4.0.