I've constructed a couple monoliths.
In 2011 my friends Dave, Ben and I did a group 2001: A Space Odyssey halloween costume. Ben went as Hal (Ben if you're reading this, I could use a good photo of your costume if you've got it), I went as the monolith and Dave went as Dave. We won an Adult Swim Halloween costume contest at Higher Ground.
I constructed my monolith costume out of cardboard boxes. It was a little small for me but I believe I got the proportions (precise ratio of 1 : 4 : 9) right.
In 2016 a monolith landed in a crop circle at the NASA Ames Research Center.
With an ample supply of MacBook boxes from our IT work at Singularity University, Dave and I decided to construct a massive, correctly proportioned, monolith for April Fools Day. Over several late nights at work, we obsessed over how to get the MacBook boxes to meet the correct proportions.
On March 31st we put the finishing touches on. We decided to try and make it look like it had landed in a crop circle in the back yard behind our office. Turns out crop circles are pretty hard to make, as is propping up a giant narrow box. We ended up leaning it against a chair to prevent the faintest of winds from blowing it over
The next morning I came in extra early to make sure it still stood. It did! We didn't tell anyone it was us. The head of HR posted to the company Slack the image below with the caption, "Something strange is afoot in the back yard!"
We got some likes on instagram posts from Roy and the official Singularity University account.
Sadly, the next day the backyard was weed-whacked. The grass clippings that landed onto the monolith baked into it in the hot sun. It was impossible to remove the grass without also removing the paint. Discouraged we leaned the monolith against the building, where it languished for a while before disappearing... until next time...