A blue circle in the air, a magic doorway?

The Hunter's Moon is a novel by O.R. Melling about two teenage cousins, one Irish, the other from Canada, that set out to find a magic doorway to the Faraway Country, where humans must bow to the little people.

He has handed us a map to his own -magic doorways.

You say you saw me in some sort of magic doorway which is now gone, and that I was in Macy's, and that I was stealing.

An onlooker might have thought it had a magic doorway.

He is told he must travel to land of Kolyma to find the magic doorway that leads to the enchanted realm.

His racing heart calmed when he heard the click of the door behind him, for it was a magic doorway with several holding and warding spells in place.

With a sharp slap of its barbed tail, the creature sped him through the magic doorway.