Driving Stopover between Lisbon and Barcelona.

I don't know how small the stopover point needs to be or what route you plan to take, but I took a look at ViaMichelin's routing suggestions and can report liking these places:

Northern route: Ciudad Rodrigo (quite small), Salamanca, Burgos, Zaragoza

Middle route: Trujillo (even smaller and quite interesting), Alcala de Henares, Zaragoza

Southern route: Not much help here. Merida (also on the middle route) has some Roman ruins and quite a nice archaeological museum, but it's otherwise not a particularly attractive place.

I do not claim the places I've listed are the best options, just good ones I happen to have visited, and they're on the way.

So you're going to rent your car in Portugal and return it in Spain? Just curious as to what that dropoff fee in a different country will be. Typically, people try to avoid that.

Google Maps shows the fastest route (Lisbon-->Badajoz-->Madrid-->Zaragoza-->Barcelona) as being 1247 km and about 11 hours of driving time. Any other route will likely be longer.

You might check Rome2rio for other options. It's not perfect, but it says that the distance for the same route is about 777 miles, taking about 12 hours of driving time and costing between 150€ and 230€ for fuel. Rental costs and potential tolls are extra.

As fate would have it, Madrid is almost exactly the halfway point, so you could pinch open the map using either resource and find a small town to stay in west of Madrid. Toledo isn't large, but it will have lots of tourists.

Talavera de la Reina isn't very small, but it might work.

I totally understand the fun of driving and have navigated in a few European countries while my husband drove, but IMHO this is a pretty long distance for only one overnight stay. I'd take it a little slower, dividing the drive into 3 days and 2 nights, allowing for a night west of Madrid and one east.

If you're only interested in getting from Lisbon to Barcelona, flying would be the best option. I'll be flying from Porto to Barcelona on June 14th. It will take about 2 hours flight time (time zone change between Porto and Barcelona). With the time at both ends required around flying, I'm figuring a total of about 5 hours for the transfer.

Have fun with the decision-making and enjoy whatever choice you make.

Thank you both for you suggestions. These are great ideas for me to look at!!

To clarify - this is at the end of our trip so we will have done much of our preferred towns/sights. We will be renting the car in Spain and returning it in Spain.