"Roscón de Reyes" is a traditional dessert, served the day of “Reyes” or Epiphany, January 6th, the day when children in Spain receive gifts from the "Reyes Magos" or Three Wise Men or Magi. The 3 kings who brought baby Jesus gifts: Gaspar, Balthasar, and Melchior.
It is traditional to put at least one surprise inside the "roscon", a little porcelain figure. The person who happens to find will have good luck and will pay for the cake!
If you fancy making your own roscón here you have the recipe
ROSCÓN DE REYES RECIPE- Twelfth Night Bread Recipe