TIL. In April 1974, in the middle of the night, a small group of conspirators secretly installed a large tensegrity icosahedron made from discarded telephone poles on the campus of Twente University in the Netherlands.

It’s still there. People call it Het Ding (“the thing”).

https://www.utwente.nl/en/alumni/inspiring-alumni/ut-canon/stories/het-ding/