The detail is "where do they park?" The answer is they don't.

Shared on Facebook with the caption "Doing absolutely no favours to their international reputation, Americans have swarmed social media posts of Taylor Swift’s Melbourne concerts confused by a very obvious detail. Can you spot it?"

It's an article from the Murdoch right-wing paper "The Australian", so I won't link the original source.

Transcription:

Aerial photo of the Melbourne Cricket Ground, surrounded to its North and East by tree-filled parks, to the West by a warm-up pitch, and to the South by a train line with two pedestrian overpasses over it. Underneath this photo is the article title "The MCG show detail that has American Swifties baffled" and byline "by Sam McPhee".