Day of Castile Challenge

Hi students, today I have realized that it's the day of Castile, in fact, in the autonomous comMunity of Castilla y León they are celebrating their regional day. But, Do you know why exactly the day 23rd of April is the day of Castile? Probably it has some connection to the habsburg unit ;) Do you accept the challenge? And please, REMEMBER, today it's also the book day. Please, read, it's not very important what,when or where, but at least read something you feel motivated and inspired for, and after reading, you will feel that indescribable feeling that just a book can do! HAPPY BOOK DAY!