Required very precise engineering.

One of the structures built for the 1900 World’s Fair, which Paris hosted. It required 15,000 sq meters (162,00 sq feet) of glass.
Posted for the Ragtag Daily Prompt: Precise.
Living With Common Variable Immune Deficiency and It's Autoimmune Friends
A typical shot of Grand Avenue (Oakland, California) starting from the Purple Fountain Grass plant of yesterday’s post, and looking up the street from there. (Look to the left side of the plant and you will see the hood of yesterday’s blue car.) An unremarkable shot in general, which I was about to delete, until I saw the Ragtag Daily Prompt of Psychedelic today. Then I realized that I could have a little fun and turn the unremarkable into WOW. I hope you agree.
Posted for K’lee and Dale’s Cosmic Photo Challenge: Monochromatic.
Scaffolding has been around since humans decided to try and build higher than their arms and hands could reach. It took ingenuity to get the idea off the ground. (Sorry, that’s a really bad pun, but I couldn’t resist the temptation.) Archeologists think that scaffolding might have been used to reach the high portions of the rock in the Lascaux Caves in France. That would put the use of scaffolding in the Paleolithic era, which means that prehistoric man constructed some sort of scaffolding over 17,000 years ago. That is amazing to me, as I can’t really conceive of how long ago 17,000 years was. Additional information on the history of scaffolding can be found here.