You have to be nearby to find the Neonian Baptistry at all, a plain brick octagon beside the cathedral that looks more like a service building than a monument. It is the oldest of Ravenna's surviving mosaic monuments, built around the end of the fourth century as the baptistery of the orthodox cathedral, and redecorated in the middle of the fifth century by Bishop Neon, whose name it carries. It was raised on the site of a Roman bath house and reused older marble, typical of a city busy turning pagan stone into Christian rooms.
Look up, and the dome opens in circles. At the centre Christ is baptised by John in the river Jordan, with a bearded personification of the river holding a cloth. Around him the apostles march in a ring, their robes in gold and white against a blue sky, and below them are empty thrones and altars, framed by stucco prophets. The colours are more restrained than San Vitale's, which makes the beauty feel earlier and slightly stricter.
The floor is the quiet clue to the city's history. Ravenna was a lagoon town, and the land under it has settled while silt built up around it, so the original floor lies well below today's. Walk down a few steps and you are standing in the fifth century.
For the ride list the connection is the Vena del Gesso Romagnola and Monte Penzola, the dazzling ridge of gypsum on the first folds of the Apennines. After a morning among tesserae, the contrast is nice: a place where the geology is the art. The route there leaves Ravenna on flat farm roads and enters the hills near Faenza, where vineyards for Sangiovese and Albana, a local white, line the slopes.
Fuel is easy in Ravenna and along the Via Emilia towards the hills. The old centre is mostly closed to traffic, so park at the edge and go on foot. Coffee at a table in the square next to the cathedral costs about what you would expect from a tourist city, and is still worth having.