This hike will take you 3-5 days with amazing scenery, great campsites and lots of wildlife. There are perfect trails and alpine views that are phenomenal.
The Rockwall trail is a famous 3-5 day trek in Kootenay National Park.
We started from the North and camped at Helmet Falls our first night, and then continued south and exited out Floe Lake. I would recommend this direction for a backpack, and the opposite direction for a trail run (it's about 50k).
The scenery is amazing, trails are spectacular, and we even ran into (almost quite literally) a bear. You might not want to run down the (very small portion) of heavily vegetated trail. You tend to happen upon wildlife before they hear your heavy breathing and conversation.