Cyprian was bishop of Carthage in the middle of the third century, a former orator who converted late in life and became one of the great voices of the early African church. He argued about how to treat Christians who had given way under persecution, he stayed with his flock during a plague, and in 258 the Roman authorities beheaded him for refusing to sacrifice to the gods. The Christians of Carthage never forgot him. Over the centuries churches were built in his honour around the city, and the basilica of Saint Cyprien is associated with that memory, though what remains on the ground is modest, mostly traces of walls and columns that you need a guide or a good map to interpret.
That is the honest part, and it is worth saying that Carthage rewards slow looking rather than grand monuments. The Antonine Baths, the Punic harbours, the Roman theatre, the hill of Byrsa with its museum and the cathedral of Saint-Louis, built in the French colonial period, all lie within a short distance, and the early Christian sites fit among them. North Africa produced Tertullian, Cyprian and later Augustine, and without them the history of Latin Christianity would look different.
On the bike, the neighbourhood is a pleasure for its calm. The roads are shaded by eucalyptus and pine, sea air blows up from the gulf, and you pass villas with painted gates and gardens. Sidi Bou Said, with its blue and white houses on the cliff, sits less than a kilometre away, and the tourist traffic there can be heavy on weekends, so consider walking up the hill from the train station rather than riding. Surfaces are usually fine, though speed humps appear without warning and rainwater collects in dips after storms.
Fuel and food are no trouble. Carthage and La Marsa have petrol stations, bakeries and cafes where you can try bambalouni, the fried doughnuts rolled in sugar that people eat by the sea. Spring and early summer are comfortable, with the light at its best an hour before sunset, while August is hot and busy.