RM Castilla is the most successful reserve side in the history of Spanish football, having amassed more points in the Spanish Second Division than any other reserve side. In 1980, RM Castilla even reached the final of the Copa del Rey, Spain's premier domestic cup competition, where they lost the title to Real Madrid's first team squad.
In terms of performance in the Spanish Second Division and its participation in the prestigious Copa del Rey competition, RM Castilla stands out as a reserve side with significant success. In 1980, they reached the final but were defeated by Real Madrid's first-team squad.