"Min bedstemor er i haven."
Translation:My grandmother is in the garden.
When something is inside of a room, we seem to use på. What is the rule there? Is på only for structures?
There is not much of a rule there, but usually you're pretty well off with using i. På is mostly used for anything værelse and for some public places: på torvet (in the square), på embeden (in the public office), på slottet (in the castle).