Design of the World's Most Geeky Geocache -- The Dragon Puzzle

Nick Parlante Nov 2009 (updates July 2010)

This page has design and construction notes about the ridiculously geeky hardware hacking project that became the dragon puzzle geocache. There's some 2010 updates below and also a video below showing what it looks like and how it works.

I love the idea that you come across a mystery object with no instructions or anything. You manipulate it and look at what it does, and with luck have that Aha moment to figure out what it means (seems like a movie plot actually).

I've played around a little with the inexpensive and open source arduino microcontroller, and it's perfect for making a little battery powered puzzle. I've done a little geocaching, and I figured that would be a good the way to structure the puzzle -- you find the dragon puzzle at the first GPS coordinates, and you must solve the dragon puzzle to get the coordinates of the nearby treasure cache.

With these ideas in mind, I saw this cast iron dragon on sale for $8 at Cost Plus and knew I had found my mystery object. Like any project that looks good in the abstract, there were more a lot more issues than I had imagined in actually making it work.

Here's a closer look at the precision construction of this space-age instrument:

If you'd like to visit the dragon puzzle on Stanford campus, go to dragon puzzle page at, (you'll need to sign up for a free account to get the coordinates).

2010 Update

Here's what I've learned up through July 2010:


Here's a little video I made using my laptop's camera to show how the dragon is built and how it works (spoiler alert: in the last part of the video, I show how to solve it, but you can watch the video up to that point without spoiling the puzzle). I used the new HTML5 video tag to embed the video in the page using the new, open WebM codec. From a technical point of view, this the way video on the web should work, and as a geek I'm happy to be the early adopter for this sort of thing. To watch the dragon video you'll need a browser that supports HTML5 WebM out of the box, such as as Mozilla Firefox or Google Chrome.

There's one other subtle thing the dragon does when you solve the puzzle which, it occurs to me, is not shown in the video. You'll have to visit the dragon to see that bit.

There's also a great talk to see and an inspiration for this project: JJ Abrams Mystery Box (watch the video or just read the transcript) about how mysteries drive the plot forward in Star Wars, Lost, etc. Also, the puzzle hunt at Stanford known as The Game is an inspiration from back in the day.

Of course this whole project was just an excuse for some hardware hacking and tinkering, and I hope that people who find it get a kick out of it. This project makes no sense in terms of cost/benefit of my time. But in reality, I've gotten immense enjoyment out of it and reading the logs as people play with it, so I guess everyone needs an impractical little creative project.

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Nick Parlante