My 362 class is currently at work on a multi-part cache
Catastrophe, Calamity, Cataclysm Part 1 by rodz (adopted from Daoloth & Tuna) (GC5E4A)
Catastrophe, Calamity, Cataclysm Part 2 by rodz (adopted from Daoloth & Tuna) (GC5E4B)
Catastrophe, Calamity, Cataclysm Part 3 by rodz (adopted from Daoloth & Tuna) (GC5E4D)
Catastrophe, Calamity, Cataclysm Part 4 by rodz (adopted from Daoloth & Tuna) (GC5E4E)
Catastrophe, Calamity, Cataclysm- The Prize! by rodz (adopted from Daoloth & Tuna) (GC5E3C)
[The links above appear to be active, but aren't. I'll check this out. In the meantime, you can go to http://www.geocaching.com and search for these by keyword or by the cache number (last number in parentheses on the right)]
The first four parts take you to various parts of London en route to collecting information that will enable the analytic searcher to determine the position of an actual physical cache. Quite a variation on a theme (though the physical cache is in a Tupperware container).
We actually started with Part 4 which took us to the site of the water pump which was the source of a cholera epidemic in 1853. John Snow, the discoverer of chloroform, by the way, was the physician who actually inferred that cholera was not propagated by "miasma" (bad air), but by something in the water. By turning off the water in Soho, he closed off the source of the epidemic and the death count dropped, a stunning achievement. (It still took several years for the "miasma" theory to be fully abandoned, however.)
A central contribution of Snow was the epidemiological map showing the number of deaths radiating out from a central point (the pump on what was then 40 Broad Street, now Broderick Street). It's possible now to overlay this map in Google Earth, as well as the Greenwood map of 1827 and a London map from the Rumsey collection from about 1842. Stay tuned!