Pi is fascinating for any number of reasons, but this video does an excellent job summarizing the history of pi and how it was calculated. I knew some of it, in concept, but I would have struggled to explain it. I still wouldn't get a full explanation right, but I feel definitely more capable of attempting it. That said, rather than have me explain it, just watch the video.
In 2015, the wife and I took a trip to Italy for our anniversary and discovered the World Expo was in Milan while we were. We went and saw it, and while it was a fun and unique adventure, Cameron's blog nails it exactly - it was entirely about promoting countries and less about science, discovery, and celebrating accomplishments.
I would love to see (both metaphorically and physically) the change and re-launch of the World's Fair as he describes and outlines.