When I was in Rome a few years ago, I saw dozens of people on the sidewalk sitting in invisible chairs. They had buckets in front of them so you could show your appreciation by tossing in a few euros.
In this video, The Q (he probably regrets that name now) makes a structure that creates the illusion of an invisible chair.
Original Link: https://boingboing.net/2021/02/19/how-to-sit-in-an-invisible-chair.html
