Dan Kraft submitted the route:
Mount Si is an extremely popular hike near Seattle. Its summit is known as "the Haystack" and is a class 3 scramble. If traveling all the way to the summit, the new trail gains about 3600' in 3.5 miles.
Another route is "Old Si", via the older trail, from the Little Si trailhead to boulder garden cutoff to the old Si trail to the top (first rocky outcrop), as per this Strava segment (which doesn't include the summit scramble).