Puzzle of the Day

(Note: The last Puzzle of the Day for the 2019–20 school year will appear on Wednesday. Thanks to all my readers! I hope you've had fun!)

Can you identify these landmark structures? (Hint: They're all in the U. S.)

1. With sides of length 921 feet, Building #1 should theoretically cover an area of 1,459,379 square feet (including its inner courtyard). Fun fact: This building has six ZIP codes.
2. Building #2, standing 555 feet tall, is the tallest stone structure in the world built by humans; it's also the tallest building of its particular shape, but by no means the oldest—a distinction it misses by about 3800 years.
3. Disregarding its thickness, Structure #3 ("building" seems like the wrong word) is approximately the graph of the equation for , where x and y are in feet.

Check back tomorrow for the answer, a shoutout to all the solvers, and a new puzzle!

Previous puzzle:

The following quote from Wikipedia describes the origins of which piece of playground equipment?

"Hinton's father, mathematician Charles Hinton, had built a similar structure from bamboo when Sebastian Hinton was a child; his father's goal was to enable children to achieve an intuitive understanding of three-dimensional space through a game in which numbers for the x, y, and z axes were called out, and each child tried to be the first to grasp the indicated junction. Thus, the abstraction of Cartesian coordinates could be grasped as a name of a tangible point in space."

Answer:

It's a jungle gym:

Incidentally, for those of you who have heard of Boolean logic, its namesake (George Boole) was another member of the inventive and eccentric Hinton family. Leo S. told me about another Hinton invention: the first (baseball) pitching machine, powered by gunpowder.

Congrats to those who found this puzzle within their 🐒grasp🐒: Trent, Jessica, Atticus, Hazel, Peter M., Maddy, Harper, and Jason!