Spain itinerary advice?

Sitges or Tossa de Mar (75 minutes by top-notch Express bus from Barcelona’s Nord bus station). for the beach visit.

Palau de la Musica In Barcelona for a flamenco show— check its website for ticket information.

Zaragoza ( capital of Aragon) with its Palace of Aljaferia of Moorish origins and Roman Walls for history. Look at some photos of Palacio de la Aljaferia to get an idea of its history. Zaragoza is a stop on the high-speed train route between Barcelona and Madrid, so it’s right on your route.

Madrid for the finale. If you really are into history do a day trip on the train to Toledo—the city that was Spain’s capital for centuries.

In November 2022, I spent three nights in Zaragoza and enjoyed it. As Kenko said, the Moorish Aljafería Palace and the numerous Roman sites are interesting. The palace is outside of the historic center, but my husband and I found the walk there and back to be pleasant. Beyond the Roman related museums, there are a number of other worthwhile museums (Tapestry Museum, Pablo Gargallo Museum, Rosario de Cristal). Basílica de Nuestra Señora del Pilar is a beautiful church that dominates both the main square and the Ebro River. Mercado Central is a nice indoor market near most of the major sites.

Hi, trains are very comfortable in Spain but for sure you will enjoy much more if you connect both cities with a road trip. Zaragoza is a mid-sized city, famous mainly for El Pilar Basilica. La Aljaferia is also a must-see in Zaragoza. From Zaragoza I´d recommend you head west and get to Pamplona, where the San Fermin Fiestas take place every year in July, then Logroño to enjoy one of Spain´s best tapas districts (Calle Laurel) In Rioja I´d recommend you visit the Monastery of Yuso and also enjoy hiking, you could walk along pilgrims near Santo Domingo de la Calzada, which is an important stop in El Camino de Santiago.
An interesting next stop could be an amazing village, hardly known, called Frias. But before that, I forgot to mention that in Rioja you will be able to enjoy great local food and wines. Haro is well-known as a very interesting town for wine lovers.
From Frias you drive south to Burgos, which holds an amazing cathedral and good (but heavy) gastronomy. Further South Lerma is an interesting small town to spend a night, and I´d strongly recommend Segovia before you get to Madrid. Depending on how much time you want to spend in each place, and if you are really into food, maybe instead of driving south from Rioja you could head North to San Sebastian and/or Bilbao. San Sebastian has an amazing beach and holds lots of amazing restaurants and bars. Bilbao is home to the Guggenheim Museum, and in the old district, you will enjoy many amazing tapas bars as well. This itinerary could give you some hints for you to prepare a quality road-trip. https://privatetoursofspain.com/397/madrid-san-sebastian-and-barcelona-gastronomy-tour/

Zaragoza would be a good choice. While the Aljafería Palace is a popular place to visit and the exterior wall and initial interior courtyard very pretty, I found the remainder of the palace to be lacking in charm. After the Alhambra and Sevilla’s Alcázar, I was underwhelmed. The palace is just over a mile from Plaza of Our Lady of the Pillar.

The itinerary lechugasam (lettuce Sam) laid out would be nice if you had a rental car and would be difficult to do in a timely fashion without one. It would be easy to spend a month in that area and not see everything there is to see.

Conversely, we loved Aljaferia Palace! Late afternoon there were few, if any, other visitors. It was beautiful and peaceful (unlike the Alhambra and Alcazar of Seville which were packed to the point of unpleasantness).

Wholeheartedly agree with exploring by rental car.