Barcelona Spain & Lisbon Portugal Both For $400 Total - 2 for 1

Air Portugal Stopover Program Option
This option available to Air Portugal passengers, allows you to add a free stopover in Lisbon from 1 to 10 days. There is no other flight offer in the world that is as good as this one due to the number of nights (up to 10) allowed.

You can opt for this stopover on an outbound or returning trip. (Must book direct)

This is optional and you can just connect directly on to your final destination if you do not wish to use this travel hack to see Portugal for free, as going directly to your final destination is the same cost. Learn more on their website.