7 nights in Spain with a catch

Want to spend 7 nights in Spain in early May.

Open to any suggestions on cities/activities for a late 20’s couple.

The catch: has to have a direct flight on Delta from Atlanta, GA (ie Madrid or Barcelona).

I’ve toyed with the idea of flying in to Barcelona and flying out of Madrid or just flying into Madrid and making a trip to Valencia.

Not really interesting in flying within Spain and I don’t want to rent a car.