The 34-year-old Portuguese star's hair implant centre in the Spanish capital opened its doors in March even though he has been a Juventus player since last year.
"The Spanish people treated me well, I wanted to thank them by giving them work," Ronaldo told El Pais newspaper.
"I know that the people love me, they know that I gave a lot to the club (Real) and that they also gave me a lot."
Ronaldo, who won two La Liga and four European Champions League titles with Real, said that he hasn't ruled out becoming a coach when his playing days are over but still has his critics to defy.
"I see football as a mission: to be on the field, to win, to improve, I feel extra pressure, people always judge, they say it's over, that I'm 33, 34 or 35, and I should stop," added the five-time Ballon d'Or winner.