Give Lisbon three nights, Coimbra one and Porto two. This northbound route pairs the capital's riverfront neighbourhoods and a Sintra excursion with a smaller university city, then finishes beside the Douro. The two intercity moves fall on days four and five; the other days belong to exploring. Lisbon introduces the Tagus and Belém's maritime monuments, Coimbra brings university courtyards and student traditions, and Porto adds tile-lined streets and wine lodges across the river in Gaia. Fly into Lisbon and out of Porto if possible. Six nights make a rewarding first visit, although they do not leave room for the Algarve or a full Douro Valley day. Choose this version for city walks, architecture and food, with a different setting at each overnight stop.