This seven-day rail trip gives you three very different city holidays in one journey south. Paris opens with the Seine’s island neighbourhoods and a morning among the Louvre’s collections. In Lyon, the scale becomes more intimate: Renaissance courtyards, two riverbanks and the traditional restaurants called bouchons. Nice brings Baroque interiors, a produce market and a walk beside the Baie des Anges. Spend nights one and two in Paris, three and four in Lyon, and five and six in Nice; leave from Nice on day seven. That makes room for one full sightseeing day in each city and lighter arrival afternoons. Choose May, June or September for the mix of outdoor walks and indoor visits; April and October also suit sightseeing. Swimming is an optional addition, rather than the purpose of these two Riviera nights.