8.5 very steep miles round trip to a fire lookout with an extraordinary view. Despite the relentless elevation gain, this is my favorite hike in the park. See
https://www.wta.org/go-hiking/hikes/shriner-peak. Also check out this cool 360 degree view:
https://www.360cities.net/image/shriner-peak-fire-lookout-mt-rainier-national-park-wa-state