Okay, we saw it in HD, which you might consider cheating because we could see the stage both in wide angle and in pretty tight closeup.
If you could see the Ferris Wheel at the back of the stage (stage right; on the left looking from the house), you should have been able to see the tiny balloon gondola at one point on it; early on, iirc, baskets for gondolas were visible all around the perimeter. When Fiordiligi was singing that aria, it was very clear that she was in a full-size version of the balloon-topped Ferris wheel gondola; the motions of the two paralleled each other. She was definitely NOT in the basket of a hot-air balloon.
Maybe if you saw the original Broadway production of Albee's Tiny Alice, you'd get it. Same idea of a full-size bit of décor paralleling the miniature. But you weren't born yet, were you?
We thought the singers were fabulous, even O'Hara. Excellent acting (well, O'Hara was more Broadway than opera house on that, but that was a directorial decision, I guess). We saw both Majeski and Malfi in Le Nozze di Figaro a few years ago (The Countess and Cherubino, respectively), and love them both. And I love David Robertson about equal to Esa-Pekka Salonen.
My only negative is probably because of the way the HD shows the principals: anyone close by in the background is highly noticeable as well. Which meant that sometimes, the skill set performers were perhaps a bit too visible, and a little distracting. Otherwise, we thoroughly enjoyed it.