A Geocache is a treasure hidden by high tech adventurers expressly to be found by the like minded armed with handheld GPS receivers. The Geocaching.com web site explains the sport and can point you toward stashes in your own locale. These are the caches we have created.
Geocaches Installed in 2001 45.59848, -123.36386 The Burn Geocache 45.29668, -123.95034 Sand Lake Geocache BOUNDARY 45.522777, -122.675727 Portland
The official website reports, There are 16,439 geocaches near Beaverton, Oregon. And millions more around the world. Start looking. Login required. site 
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See Portland Confluences for which I was first to visit.