Basel (Jan 4, 2023):
Strasbourg (France)
Obernai (France)
Dambach-la-Ville (France)
Sélestat (France)
Haut-Koeningsbourg Castle (France)
Bergheim (France)
Ribeauvillé (France)
Hunawihr (France)
Riquewihr (France)
Kaysersberg (France)
Turckheim (France)
Eguisheim (France)
Colmar (France)
Basel (Switzerland)
Zurich (Switzerland)
A brief history of Basel:
Origins:
Basel originated as a Celtic and later Roman settlement called Basilia, situated at a strategic point on the Rhine River. Even in antiquity, it was an important trade crossroads.
Middle Ages:
During the Middle Ages, the city grew around its cathedral and became a prominent religious and academic center. Its university, the oldest in Switzerland, was founded in 1460 and attracted humanists such as Erasmus of Rotterdam.
19th Century:
In the 19th century, Basel established itself as an industrial and commercial center, particularly in sectors such as chemicals, pharmaceuticals, and banking. Its border location reinforced its economic and cultural role.
Present:
Today, Basel is one of Europe's most important cultural cities, renowned for its museums, modern architecture, and international fairs such as Art Basel. It is also a major hub for the pharmaceutical and research industries.
We didn't like Basel; it's more expensive because it's close to Zurich, but it's not as worthwhile as the rest of Alsace; it only has two streets to visit.
Overall summary: this route is worth doing by car.
Hotel Basel: Spalenbrunnen Hotel & Restaurant Basel City Center (1 night without breakfast). There's no parking nearby and the streets are toll roads. It's a hotel to avoid because it was rather disgusting, even though it was spacious. The bathroom was tiny and had an AC unit. It's only good for sleeping and little else.

We took the flights through Trip.com with Air Europa.
Madrid-Frankfurt flight: €30/person.
Zurich-Madrid flight: €58/person.
Car rental with Vip cars: €78 (2 full days).
Hotel Basel: Spalenbrunnen Hotel & Restaurant Basel City Center (1 night without breakfast): €128 for 2.
Information obtained from the web https://www.exteriores.gob.es
Passport/ID: Both are valid.
Visa: It is not required for Spanish citizens.
European Health Insurance Card: It's necessary, it's very easy to order online and they send it to your home. Request.
Vaccines: There are no mandatory vaccinations for entry.
International driving permit: It is requested through the DGT website.
It costs €10.51. The good thing is you can order it online and pick it up without an appointment. It took a couple of days for ours, then you go to pick it up and it's a cardboard card like the ones they had 20 years ago.
Payment card/currency exchange: we always go with Revolut definitely.
Roaming: EYE! NO. It's very important to turn off your mobile data because they'll rip you off. We didn't even cross the border, and since it connected to their network, the "gift" was €50 for less than a minute of use on Lowi.
GPS: Maps.me Download the maps of Switzerland in Spain and they work great offline, whether you're on foot, by car, or on public transport.
Where to eat: If you want to eat at a restaurant, there's also the app. TheFork which has many discounts. If you book with the code 7C1B79A3 When you are finishing the booking, you will get 1000 Yums = €10 discount at your next meal. In addition to other special offers they often have, or simply to accumulate points and use them for discounts on your next payments.
It operates in several countries, including Spain, France, Italy, the United Kingdom, the Netherlands, Belgium, Switzerland, Portugal, Denmark, Sweden, and Australia.