The hollow dead oak spire that rotted to soggy dust in Wingra Park and was finally sawed to a stump three weeks ago by city parks workers held a treasure, one of 833,189 such treasures in the world. This one can be found at 43 degrees 03.421 minutes north and 89 degrees, 25.524 minutes west.

Welcome to the world of geocaching, which is the skill of appearing to be lost, but knowing exactly — within a few minutes or seconds, anyway — where you are.

That tree hid a plastic film canister that contained a written log of who had been there and when. It was placed there by Dane Stenson and Lindsay Tratz, participants in the increasingly popular world of geocaching, a "worldwide game of hiding and seeking treasure" using Global Positioning System technology and the Internet.

David and June Klann of Madison, who until last week had found a treasure for 25 consecutive days, have hidden caches in the Dane County parks. Patrick and Martha Barlow, of Waunakee, got to know Mexico better by geocaching on vacation.

And Peter Biermeier has for the past five years introduced his son, Dillon, to the hiking trails of Wisconsin by looking for geocaches all over the state.

He estimated there are more than 4,000 caches hidden on state land, including parks, out of the more than 11,500 located in the state. Biermeier, who is the Department of Natural Resources liaison with the state geocacher organization, said park officials welcome geocachers, who follow a "cache in-trash out" philosophy and get permission before placing caches on public property.

The growth parallels the increased access to GPS devices. In 2002, there were an estimated 150 caches in the state, now there are more than 300 in Madison alone.

Dane County requires geocachers who place the caches to buy a permit — $25 for three caches — just to keep track of where they are. The city requires registration, but no permit, and the state requires registration. Many thousands of other caches are simply publicly placed and never, ever buried.

What’s in the caches? David Klann puts marbles in the treasures that he hides. The general rule for such finds is: If you take one, leave one.

Klann has found caches hidden in plastic birds on tree limbs. Martha Barlow recalls finding one in a fake pine cone attached to a fir tree full of pine cones.

Occasionally, a cache gets "muggled," which is what happens when a "non-geocacher" finds a treasure and destroys or moves it, often unknowingly. It turns out the Madison parks workers who found the cache in Wingra Park were helpful muggles. They carefully put the treasure in a new hiding place. Where? Start at 43 degrees 03.421 minutes north and 89 degrees, 25.524 minutes west.