Apparently, there are millions of them hidden all over the world - from Rome to Rio and from Timbukto to Tokyo.
And, pretty, soon, it looks certain they will encircle the whole of Horncastle too.
According to reports, geocaching is a craze that is sweeping the nation.
In case you are wondering, geocaching is an outdoor recreational activity which essentially involves walkers tracking down hidden containers.
The containers - usually a Tupperware box - are called “geocaches” or “caches” and contain a logbook and a gift, the type you would normally find in a Christmas cracker.
Competitors track down the boxes, sign the log book, take one of the gifts and replace it with another.
Determined not to miss out, Horncastle’s Walkers are Welcome Group has called in something of an expert to plot a course - and hide some caches.
Annie Stiles, a 21-year-old who is studying at Lincoln University, has already started the task.
She is focussing on a ‘Round Horncastle’ route that covers around 14 miles - with, thankfully, a few shorter options.
Initially, Annie will hide boxes on a couple of sections, but it is hoped to eventually include the entire 14-miles for real geocaching enthusiasts.
Annie said: “It’s a big craze and loads and loads of people are doing it.
“I’ve completed a number of special routes although I’ve not set one myself.
“However, I’ve walked some of the route around Horncastle and it’s brilliant.
“I think there are already a few caches hidden but I aim to put about 40 in place at first.
“Then, we’ll build on that. When it’s finished, Horncastle should be completely ringed.”
Anyone taking part will need a map - and preferably a Global Positioning System (GPS) - to track down the various caches.
It is also hoped to introduce a special ‘app’ - just for the Horncastle route which takes in the town and several surrounding villages including High and Low Toynton and Mareham on the Hill.
The first caches should be in place for the launch of the Wolds Walking Festival next month.
There is a serious side to the idea as the town’s Walkers For Welcome Group believe geocaching will attract hundreds of new visitors.