My wife and I will be on an 11-day Douro River cruise, starting in Lisbon and ending in Porto on a Sunday morning in late May. We must be back in Lisbon Thursday afternoon. I am looking for suggestions on where to go for those 4-5 days. Thank you.

spend half- in Porto and half+ Lisbon, go to Evora and go walking in Alentejo

And I'd like to join the conversation. Going to Lisbon for a week and was thinkoing about visiting Porto too. What about transfer from Lisbon to Porto? Trains or buses? Last time I spent just 3 days in Lisbon and didn't go anywhere else. =)

Catch the train in between Alice, very comfortable in 2nd class. Porto has sort of two centres, around the main square and railway station is one and then down on the river bank where the port lodges are. Then there is a part of Art Deco style and the local tourist office offers trips up the river to see where the grapes go. Makes fo2 to 3 good days.

Lisbon is a little chunkier and better transport links, you can probably walk the best bits of Lisbon in two days, but then go off and visit the southern area. You need a rough guide to Portugal to understand this.

https://www.cp.pt/passageiros/pt click on the En for English
and seat61.com to understand the options

Sorry, I will try to be more clear:

The cruise part is -
Days 1-2 Lisbon
Day 4 Coimbra & Porto
Day 5 Porto
Day 6 Castelo Rodrigo
Day 7 Salamanca
Day 8 Pinhao
Day 9 Porto
Day 10 Porto-Guimaraes
Day 11 Porto (Sunday)

So, for the next 4.5 days, where would you suggest we go, knowing that we have to be back in Lisbon Thursday afternoon? We are open for car, rail, or train. We don't want to duplicate any of the above. Thanks.