What cities are best to visit in Spain during the days between Christmas and New Years?
Madrid, Cordoba, Seville, Granada
we enjoyed Sevilla and Madrid during xmas wk. it was very cold so plan for it.
We were in Spain last Dec 18-28. I suggest Seville, Granada, Madrid. You will likely have better weather in Andalucia than in Madrid. We lucked out and had great weather in Seville and Granada (long sleeves, but no jacket needed), but I don't think you can count on those warm temps. Bring layers (including layered outerwear) because the weather will be unpredictable, and what you experience in Seville or Granada will be different from Madrid.
I was very happy I had along my light, silky long underwear. The hotels have heat, but none of the ones we stayed at seemed to keep the room toasty warm at night and the blankets were pretty lightweight. So my long underwear served as my pajamas.
Wherever you go, it will be fabulous. ENJOY!