What it is
The medina of Tunis is a UNESCO-listed old city that is still lived and traded in, smaller and less overwhelming than Fes. The Bardo Museum holds one of the world's largest collections of Roman mosaics, lifted from sites across the country. The Carthage sites, about 15 km north and reached by the TGM light rail, are separated parcels: the Antonine Baths on the sea, the Byrsa hill, the tophet, the cisterns.
Why go
The Bardo is the single best argument for coming to Tunisia, because it gathers in one building what was cut from floors across the whole country. The medina is the most manageable in North Africa for a first-time visitor.
When to go
Any month outside the July-August heat. Confirm the Bardo's opening hours and status close to your dates rather than assuming; it has had extended closures in the past. Carthage in the middle of a summer afternoon is exposed and shadeless.
Most people stay 2-3 nights.