Kroos left Bayern Munich over six years ago to join the Spanish giants.
"I was lucky to come to Real Madrid as a world champion, making it clear that I wasn't a nobody.
"But winning three consecutive Champions League titles is more than I could ever imagine."
The German international also talked about his arrival to Spain and the problems he had with the language barrier.
"I must admit, I didn't have any motivation to learn Spanish at first.
"I only became more fluent in the second or third season at Real Madrid."
Kroos also had nothing but kind words to say about coach Zinedine Zidane.
"He is incredibly good at managing this group of stars, he knows all the players at eye level and has everyone playing for him," he explained.
"He is also very good technically."