The cleanest mainland route runs from Lisbon to Porto. CP's Alfa Pendular and other long-distance services make that corridor practical, and Coimbra, Aveiro or the Douro can be added with a real decision about how much moving you want to do. Lisbon deserves several nights because its most useful side trips—Sintra, Cascais and the river-side monuments—compete with the city itself. Porto needs less time to orient yourself, but the riverfront is only one part of it; leave a full day for the city before turning it into a Douro transfer.
Do not treat the Algarve as the final box on the same itinerary by default. It can work after Lisbon by rail, but the best base depends on the coast you want: Lagos for cliffs and western coves, a resort area for a stay centred on one beach, or Faro as an airport and lagoon gateway. A car adds range for secluded beaches and rural inland stops; it adds little to a city pair where parking and historic-centre streets become the day's main task.
Madeira and the Azores need their own logic. Funchal gives Madeira an urban base, but the island's value lies in the terrain beyond it. Ponta Delgada does the same job on São Miguel, where crater lakes and viewpoints are not city-centre attractions. Fly in, plan the driving or guided days, and reserve enough nights for weather to change rather than building an island visit around one guaranteed panorama.
Portugal has a dense cultural map, including World Heritage places in Lisbon, Porto, Sintra, Coimbra, Évora, the Douro and Madeira. Use that richness to choose a corridor—not to collect every designation. A Lisbon–Porto route can hold Belém, Sintra, Coimbra and the historic centre of Porto; an Alentejo or Douro route deserves its own slower travel days.
Season changes the route more than one national forecast suggests. Official climate information distinguishes the mainland from Madeira and the Azores, and conditions also vary between Atlantic coasts, the north and the hotter interior. Spring and autumn suit city walking well, while summer is a stronger fit for beach and island days if you plan around demand and midday heat. Check the current operator or local forecast before committing to a hike, boat trip or a long scenic drive.
For food, let the region decide the meal. Lisbon's markets and neighbourhood restaurants, Porto's river-city cooking, Algarve seafood, Madeiran produce and Azorean dairy and fish all make more sense in place than a generic national tasting list. Pick a hotel that lets you eat where residents and visitors actually gather, then use one memorable meal to anchor the day rather than chasing every famous dish across town.
Lisbon
