You are looking for a glass jar. this is one of two geocaches in frog holler park.
The park is along the shoulder of Wax Orchard Road. walk along a short stretch of forest road which ends at an informational kiosk. This marks the beginning of the trail network. There are a variety of short trail segments that wind through this park, so a map will be helpful in keeping track of all the turns (find one on the King County Parks website).
A partnership between King County Parks and the Vashon-Maury Island Land Trust made the acquisition of this public land possible, and they continue adding new acreage to the park.
These trails are open to hikers, mountain bikers, and horseback riders, so be sure to follow proper trail etiquette when it comes to yielding to your fellow trail users. And please be mindful of park boundaries as this area is bordered by private land.