The empty donut around Madrid is often referred to as "La España Vaciada" or the "hollowed out Spain". The centralizing policies in Spain during Francoism led to the abandonment of all of Castille except the towns lucky enough to be connected by highway to Madrid.

Ask anyone born in the Madrid metropolitan area what's their pueblo, the majority of people are 1 or 2 generations removed from their rural origins and many still travel yearly to the village where their grandma/grandpa lived.

This came with the erasure of the cultural identities of all the people arriving, not having cohesive communities and being absorbed instead by the metropolitan atmosphere, forgetting their traditions or just leaving them as something to be enjoyed just a few weeks a year when they go back to their pueblo.

Any serious socialist movement in Spain must understand the conflict this created and still creates, and how a future socialist Spain likely relies on the urbanization and industrialization of this hollowed out Spain, using the local resources (whether that be mining, agriculture, energy, etc.) and creating a less centralist network providing services, welfare and capital to all areas of the country and not just to the very centre.