The Neonian Bapistry is an octagonal baptistery built in the 5th century. As the oldest building in Ravenna, it is a UNESCO World Heritage Site and contains some of the city's most beautiful Byzantine mosaics.
It was built as part of Ravenna's orthodox cathedral built in the early 5th century but no longer stands in its original form. The baptistery was converted from an old Roman bath-house, beginning under Bishop Ursus around 400 AD.
The building was finished by Bishop Neone (451-75) in the second half of the 5th century, during which the mosaics were added to the dome. It is from this bishop that the Battistero Neoniano gets its name.