I came across this fascinating American produced video about empty Spain aka "deep Spain". I think it does a great job explaining the unique phenomenon of empty Spain, which I think many foreign tourists are totally unaware of when they visit the county.
Heres' the link: Why 70% of Spain is Empty - RealLifeLore
The basics are 90% of the population of Spain live in 30% of the country (mainly along the coast), the other 70% is inhabited by only 10% of the population!
That 70% of Spain has the same population density as Norway. One can go even further as there are wide swaths of Spain, like the Serranía Celtibérica (about the size of Ireland), that has about the same population density as Lapland! The video goes on to explain the history and socio-economics behind phenomenon empty Spain.
I think this is potentially a great opportunity for those foreign visitors to Spain (who have been 1-2 times already) to broaden their horizons as there is a lot of Spain left undiscovered. One example in the video is of the ancient town of Teruel in southern Aragon, which is known in Spain for its preserved Moorish/Mudéjar architecture, even being a UNESCO World Heritage Site, but is virtually unknown outside of the country.