Where was Heidi living and who brought her to the mountain?

Before the events of the story, Heidi lives with her Aunt Dete in Maienfeld, Switzerland. Heidi is an orphan, so her mother's sister was the relative who chose to care for her. However, Dete is a rather selfish person. She views Heidi as a burden and resents being saddled with someone else's child, even if that someone else is her own sister. She would rather go to the city and find work as a maid, so she is the one who takes Heidi to the mountain to live with her paternal grandfather.
Dete's leaving Heidi with grandfather initially seems to promise only more of the same for the orphaned girl, since her grandfather is a bitter man only concerned with his own pain. However, he grows as a person due to his relationship with Heidi and becomes a better man through her influence.