I spent three years deeply immersed in Puzzleland writing my book The Puzzler—a memoir of my lifelong obsession with puzzles of all kinds, featuring adventures to global puzzle hotspots, the history and science of puzzles, and how puzzles can make us better thinkers and happier people. (There are also tons puzzles the reader can solve, and a contest!) In the course of my journey, I looked at everything from Rubik’s Cubes and crosswords to anagrams and ciphers.
Based on that research, here are my highly subjective choices of the 10 greatest puzzles of all time. I based my selections using criteria such as ingenuity, staying power, the puzzles’ effect on history—and whether they gave me a good kind of headache or bad kind of headache.
1. The Original Box You Have to Think Outside Of
You’ve heard the cliché “think outside the box.” Now meet its likely origin: The Nine Dots Puzzle.
Connect all nine dots without lifting your pencil from the paper in as few straight lines as possible.
If you’ve never solved it, pause here. Spoilers ahead.
The Nine Dots Puzzle has been around since at least the early 1900s, with some attributing its existence to British puzzle genius Henry Dudeney.
The answer, for those who haven’t seen it, is that you can connect the dots in four straight lines, but you have to use lines that go beyond the perimeter of the square. In other words, you must “think outside the box.”
In the 1970s, business consultants started using the puzzle as shorthand for innovative and unexpected solutions, and it eventually became a cliche and cartoon fodder (as in The New Yorker cartoon of the cat thinking outside its litter box). An alternate theory for the etymology of “outside the box” says it might come from something called the “Duncker’s candle problem,” but the nine dots puzzle is the more commonly cited candidate. And the puzzle has stuck around for a reason: It’s a deceptively simple stumper that forces you overcome your assumptions.
2. The Puzzle that (Helped) Save the Free World
How can I not include a puzzle that helped us defeat the Nazis?
In the early 1940s, the British newspaper The Daily Telegraph received a letter that issued a challenge: If someone could solve a crossword in less than 12 minutes, the author wrote, he would donate 100 pounds to charity. Twenty-five participants were invited to the Telegraph’s offices, and the puzzle was drawn out of a hat. Just five of the competitors managed to solve the cryptic in less than 12 minutes—a number that was reduced to four after a participant was disqualified due to a misspelling.
Later, the winning puzzlers received a letter offering them a job at Bletchley Park, a top-secret facility where hundreds of people worked to break German codes during World War II. As one solver later recalled, “I was told, though not so primitively, that chaps with twisted brains like mine might be suitable for a particular type of work as a contribution to the war effort.” The puzzle was a secret recruiting tool to find brilliant brains to help crack the Nazi’s Enigma code—which the Allies eventually succeeded in doing.
The Telegraph printed the cryptic in the newspaper the day after the contest, and challenged readers to try to take on the task themselves. (Whether the paper was in on the true reason for the challenge is unknown.)
For the record, when I tried solving it, it took me far longer than 12 minutes—taking care of any fantasies I might have had about being a codebreaker. This is partly because the clues are, as you would hope, filled with tricky wordplay. For instance, 17 across is clued as “Is this town ready for a flood?” and the answer is “Newark.” As in New Ark. Get it? (I didn’t.)
3. The Rubik’s Cube on Steroids (a.k.a. The Octahedron Starminx)
Let me throw out some numbers to show why the Rubik’s Cube (and the beastly puzzles it has inspired) has to appear on this list: The original Rubik’s Cube has sold an estimated 450 million units.
It’s got six sides, six colors—but a mind-boggling 45 quintillion possible arrangements. So passionate are its fans that one has solved it in a record 3.47 seconds. The Rubik’s Cube has even inspired one incredibly terrible 1980s Saturday morning cartoon (theme song by Menudo).
Hungarian architecture professor Ernő Rubik invented the cube in 1974, and this simple but challenging puzzle has been a favorite ever since. And thanks to the internet and 3D printers, we are actually just now in the Golden Age of Rubik’s Cube spinoffs.
Actually, “cubes” isn’t the right word. They are mutants, as if a normal Rubik’s Cube gave birth after having been exposed to high doses of radioactivity in the womb. There are 12-sided ones, star-shaped ones, ones that change color when you turn the sides.
For my book, I bought a beast called the Octahedron Starminx from French puzzle designer Grégoire Pfennig (above). It’s a puzzle so hard that he himself hadn’t solved it. I finally solved it—well, sort of. I enlisted the help of teenaged Rubik’s champ Daniel Rose-Levine, and he solved it. But I was involved!
4. The (Possibly) Hardest Logic Puzzle Ever
There is a delightfully nerdy debate about which logic puzzle is the hardest logic puzzle ever written. I’m going to with one of the top contenders, The Three Gods Riddle, written by logician Raymond Smullyan and published in 1996.
I’ll be honest. I wrestled with it for about an hour and then broke down and looked at the answer. But I wanted to include it because it’s just so deviously complicated, and because Smullyan was a legend in the true/false puzzle genre. See how you do:
“Three gods A, B, and C are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language, in which the words for yes and no are da and ja, in some order. You do not know which word means which.”
Here’s a guide to the answer (yes, the answer needs a guide).
5. The Puzzle the CIA Can’t Solve
The world is filled with tantalizing, unsolved puzzles (for instance, the Voynich Manuscript, Minoan Linear A alphabet).
But my favorite unsolved puzzle is called Kryptos, a sculpture installed in the Langley, Virginia, headquarters of the CIA. The main part of the sculpture is a nearly 12-foot-tall by 20-foot-long copper wall. But the twist is, the sculptor teamed up with a retired CIA cryptologist to create a super-difficult cipher consisting of more than 1000 letters, which he carved into the brass sculpture. The sculpture was unveiled in 1990, but it’s only been partly solved: Three of the four ciphers have been cracked separately by enthusiasts and the CIA. But the 97-character fourth passage—called K4 by fans—remains a maddening mystery.
6. The (Possibly) Hardest Jigsaw Puzzle in the World
For my book, I also went in search of the hardest jigsaw ever, and though there are several contenders, I have to go with the infamous Olivia puzzle.
Olivia is manufactured by a Vermont-based company called Stave, which produces gorgeous hand-carved wooden puzzles renowned for their deviousness (they have uneven borders, there’s no cover image provided, boxes include pieces from different puzzles, etc.). Stave’s fans include Bill Gates—which makes sense, because they’re not cheap: Olivia costs nearly $2500.
Olivia’s trickery derives from the fact that the pieces can fit together in multiple ways. Stave says there are 10,000 possible arrangements—but only one, in which the octopus Olivia fits inside the coral reef, is correct.
Olivia is so frustrating that Stave won’t sell it to just anyone—you have to work up to it. (If you try to buy it, expect a phone call from the company. They're going to vet you to make sure you know what you're getting into.) “We want to lure people into the depths of misery,” founder Steve Richardson told me.
My niece and I finally did it, after several days in misery, but only thanks to copious hints.
7. The First Crossword
The first official crossword (at least according to most puzzle historians) was written by a former concert violinist named Arthur Wynne and appeared in The New York World in 1913. And judged by today’s standards, it kind of stinks: Not only does it use one word as an answer twice—which is a major no-no—many of its clues are ridiculously arcane. The answer to the clue “fibre of the gomuti palm,” for example, is DOH, a word most of us likely associate with The Simpsons. (Fun fact: Wynne initially called his creation a “word cross” puzzle; we get “cross word” from a typographical error that occurred several weeks after the first puzzle.)
But I felt I had to include for its innovativeness alone. It was the genesis of my favorite puzzle genre. Wynne’s creation kicked off a crossword fad—not only did the puzzles appear in books and newspapers, they were also the subject of a Broadway play as well as a surprisingly catchy hit song called “Cross-word Mamma, You Puzzle Me (But Papa’s Gonna Figure You Out).”
8. The Simple Wooden Box from the Japanese Master
While researching my book, I stumbled onto a worldwide cult phenomenon: Japanese puzzle boxes—handcrafted, wooden works of art doubling as puzzles, which have been made in Japan for centuries and typically served as storage for valuables. But those boxes were simple compared to modern puzzle boxes: Opening them requires figuring out the right combination of spins, twists, and turns and discovering hidden panels … which open to reveal yet more hidden panels or drawers. Some boxes only pop open after 150 moves. High-end puzzle boxes are collectible and can go for as much as $40,000.
The modern puzzle box era dates back to the early 1980s, when a man named Akio Kamei took the art form to new levels of complexity.
One of my favorites of Akio’s is The Die Box (above). It’s not the hardest, but it’s simple and clever and gorgeous. To solve it, you have to turn the die’s sides from one to two to three, and so on. On six, the box will open up. When you turn the die, you are causing a small steel ball inside the box to make its way through a maze to release a latch.
9. The Naughty Riddle from Medieval Monks
Riddles are perhaps the oldest and most widespread forms of puzzles, appearing in almost every culture. Some of my favorites are from a 10th-century tome compiled by monks called The Exeter Book, which features a few delightfully naughty puzzles. Take, for example, Riddle Number 25:
"My stem is erect, I stand up in bed,
hairy somewhere down below. A very comely
peasant’s daughter, dares sometimes,
proud maiden, that she grips at me,
attacks me in my redness, plunders my head,
confines me in a stronghold, feels my
woman with braided hair. Wet be that eye."
The answer is obviously … an onion, of course. The eye is wet from crying—get your mind out of the gutter.
As riddle scholar Megan Cavell, associate professor at the University of Birmingham, explained on a recent podcast, riddles were a “safe space where you could explore taboo topics. … where you have freedom to explore sexuality even though you are a monk and you’re not supposed to be exploring your sexuality.” If anyone accused the monks of being saucy, they could easily deny it: “If you solve it wrong, if you solve it sexy, then bad on you,” she said.
You have to hand it to those tricky monks!
10. Not Your Average Sudoku
Sudoku began its life with as a puzzle with the dull name of “Number Place” in a 1979 issue of Dell Pencil Puzzles and Word Games. Few noticed. That is, until Japanese puzzle publisher Maki Kaji renamed it sudoku in 1984, made some adjustments, and launched a global phenomenon.
Most sudokus you find in newspapers and online are either partially or fully computer-generated. But true Sudoku lovers say that the best Sudokus are handmade by humans, the puzzle equivalent of artisanal Brooklyn pickles. The most ardent even call them works of art that tell a story and move you emotionally.
Sudoku champion Thomas Snyder is renowned for his elegant puzzles, such as the one above from his book The Art of Sudoku. More can be found at gmpuzzles.com.
BONUS: The Puzzle That Will Outlast the Earth
Please forgive me, but I have to include a puzzle that I helped create. For my book, I teamed up with Dutch designer Oskar van Deventer and we created what we believe is the hardest puzzle ever. Or at least the most time-consuming.
While researching, I fell in love with a type of puzzle called the Generation Puzzle. This is a puzzle that takes so long to solve, you have to hand it down from one generation to another. When I began the book, the record for hardest generation puzzle was held by a 65-ring Chinese ring puzzle. These kinds of puzzles are recursive puzzles—they gets exponentially harder. For a Chinese ring puzzle, you have to remove all the rings from the rod, which is easy when there are three rings. But when there are 65 rings, it takes an astounding 30 quintillion moves.
Oskar and I set out to beat that. And the result is a puzzle called Jacobs’ Ladder. It’s a wooden puzzle with a corkscrew rod inside. The goal is to remove the corkscrew rod from the tower. But to do so, you have to twist the pegs. Many times. As in 1.3 decillion times. If you twisted one peg per second, all the visible light in the universe will have vanished before you solve it.
Part of its purpose is to remind us that the future of our species could be very, very long—as long as we don’t blow each other up.
I've done about 430 of the 1.3 decillion moves. Only 1,298,074,214,633,706,907,132,624,082,305,570 (or so) moves to go!
For more history and puzzles like these, check out The Puzzler, out from Crown Publishing on April 26, 2022. You can order it here.