In 2023 there was a giant cube made out of IBC water tanks. You can see a video here: https://www.youtube.com/shorts/FTwpt0OuW_U

This is actually what I was thinking of when I made this comment. I witnessed someone in some position of authority (from either DPW/Artery/someone else clearly sent to check it out) on the first day talking to one of the artists. They were literally watching people climb it and were like "yep, that looks pretty dangerous" and then went on their way.

It felt safe-ish to climb at first, until about halfway up when you could feel it swaying back and forth in the wind. I am usually the "climb dumb shit at Burning Man" type, but had my stomach drop about 3/4 of the way up and had to abort. It was very easy to grip, nothing felt insecure, etc, so it was definitely "safe" if you knew what you were doing. But if you ate it off the top of that, you'd be fucked.

Never been, but the titular burning man installation comes to mind.