Mercer Island, like a number of communities in the west, has a Pioneer Park of its own (not to be confused with La Conner's or Walla Walla's, among others.) The park offers a dense network of forest trails with tall trees and a lot of moss, ferns and some seasonal wildflowers. All the trails are open to hikers and bicyclists; some also are designated for use by equestrians.
The park is traversed by the busy Island Crest Way and SE 68th St, dividing it into three sections. In 2006, an additional seven acres adjoining the northeast section of the park was donated to the city and now is functionally part of the park. That parcel is referred to as the Engstrom Open Space. A map for it can be found below in the Map resources.
As the map shows, every park trail has a name. However, many trail junctions in the park are unsigned. And when trail signs do exist they often don't mention the trails by name but just indicate the direction to a nearby street. Thus, while you will never be far from a street, following a planned route can be a challenge, one that requires some map reading skills.
The most interesting trails for hikers are in the far northeast corner of the park near the creek and ravine, and the hike described here is a short loop through that area. Many opportunities exist to extend your hike and explore other park trails.
Begin at the Engstrom Open Space trailhead on E. Mercer Way at the northeast corner of the park. Head up the Creek Trail as it parallels the small creek (avoid the staircase on the right -- it leads to a private residence.) Cross the sturdy bridge over the creek and continue straight on the Engstrom Loop, avoiding the trail that arrives at a sharp angle from the right (that's the Bridge Trail, and it will be your return route.)
Cross over a sometimes-swampy area on a boardwalk and head uphill toward the southeast. In about 600 feet the trail loops around and heads back in the opposite direction but at a higher elevation so you can look down toward your earlier route.
In about 500 feet come to a T-junction with the Ravine Trail. Head left there and, in another 600 feet or so, reach another T-junction, this time with the Overlook Trail.
Turn right and continue on the Overlook Trail. Pass one of the two closely-spaced junctions with the Fern Trail and stay to the right, heading past a low fence where there are views down on a lower area with very green vegetation.
A short way farther along on the Overlook Trail there is a bench with more views, and an odd sign overhead on a tree proclaiming "The Enchanted Forest, 8-27-66," although exactly what happened here on that date, now over 50 years ago, is not revealed.
Continue on the Overlook Trail and, in about 200 feet, come to an intersection with the other end of the Ravine Trail. Unless you are doing the hike extension to explore the northwest section of the park, turn right on the Ravine Trail and follow it about 500 feet to a Junction with the Bridge Trail.
Turn left on the Bridge Trail and follow it back to the Engstrom Loop just east of the bridge you crossed earlier. Then return across the bridge and follow the Creek Trail back to your trailhead.
In season you may see a few wildflowers all along the trails. The first to bloom are trilliums and bleeding hearts. Later you may see buttercups, miner's lettuce, avens, nettles, salal, salmonberries and thimbleberries. And later the bright red fruits of the thorny devil's club will be evident near the creek.
Extending your hike
Refer to your map and note the extensive network of trails in the northwest section of Pioneer Park. This area is mostly level, so it lacks the interesting terrain changes of the northeast section. But these trails offer additional forest scenery, and are well worth exploring.
To reach this section, continue northwest on the Overlook Trail and cross Island Crest Way at a crosswalk. Explore as many trails as you like here, using your map, and when you are done return via the Maple Trail and reconnect with the Overlook Trail at its southern end.
Pioneer Park also has a southeast section that you can explore. The trails there are open to hikers, but that section is intended primarily for use by equestrians, so hikers will need to be alert and yield to horses.