What could be more healthy or entertaining than a family treasure hunt, on bicycles, on a winter’s day? James Cracknell tries geocaching.

from telegraph.uk:
Geocaching is a hi-tech treasure hunt that is a long way from Anneka Rice, skin-tight jumpsuits and helicopters. It owes its existence to computer and GPS technologies that enable anyone to find ''treasure’’ left at specific coordinates by others.

The treasure, or ''caches’’, are normally small Tupperware or ammo boxes containing a logbook and small items for trading. At the time of writing there are 953,077 active caches in more than 100 countries on all seven continents. Locating them requires a hand-held GPS or a GPS-enabled phone.