Porto

Late spring (May, June) and early autumn (September) are mild and much drier than the wet season (November, March), which peaks in December, January, when Porto is more than twice as wet as Lisbon. In summer Porto is a few degrees cooler than Lisbon, so even then it stays pleasant. Be honest with yourself: winter in Porto means proper rain.

The centre is walkable but steep. Public transport runs on the rechargeable Andante card (metro, bus, partly the funicular); a 24-hour tourist card costs €7.75. Two vertical helpers: the Funicular dos Guindais (Batalha ↔ Ribeira, around €4) and the cable car in Gaia (one-way €7 / return €10) between the bridge deck and the river.

The centre is compact: two to three days covers the city comfortably (Ribeira, the port lodges, São Bento, Clérigos, Lello, Foz). Add a day for the Douro valley. Some find two days enough; Porto rewards a slower pace and at least one day trip.

All cheap and frequent by regional trains from São Bento or Campanhã: the Douro valley (Régua around 2 hours, Pinhão around 2 hours 20 mins, with the finest stretch lying between the two), Guimarães (around 1 hour 15 mins, Portugal's birthplace), Braga (around 1 hour) and Aveiro (around 1 hour 15 mins, with its canals). Sit on the right on the way out for river views.

It works fine, but watch out for the hills and stairs. Child-friendly: the cable car in Gaia, the funicular, the boulevard at Foz and the river cruises. Heads up: the upper deck of the Luís I bridge has no railings and shares the track with the metro, so keep little ones close. Port tastings are for adults (Taylor's gives children grape juice).

The historic lodges sit across the river in Vila Nova de Gaia, reachable via the Luís I bridge or one metro stop. Book ahead. Taylor's (around €25, self-guided audio tour plus three ports plus terrace), Sandeman (guided tour with cape) and Graham's (hilltop, broad tasting flight) are the well-known houses; smaller lodges taste quieter.

Put simply: Lisbon is bigger, sunnier and livelier; Porto is more compact, greener, built from granite, and revolves around port and the Douro. If you have one city trip, choose Lisbon for light and variety, or Porto for atmosphere, food and a slower pace. Have a week? Do both: the train between the two cities takes roughly three hours.