In his book Rick Steves wrote, "If, after touring Portugal, you're continuing to the Spanish destinations of Salamanca or Madrid, it's better to visit Porto and Douro Valley before Coimbra."
Why is that? Assuming we follow his recommended two-week trip by car, we'd go from Lisbon to Salema to Evora to Nazare to Coimbra to Douro Valley, then to Porto. It seemed to me that if we wanted to add in Salamanca, we'd go from Coimbra to Salamanca to Douro Valley, then to Porto, where we would fly out to return home.
How would it make sense to visit Porto and Douro Valley before Coimbra?