Key Summit is reached via an easy 6 km walk along the Routeburn Track from the The Divide Shelter on the Milford Road. The first part of the walk is through alpine forest to The Divide where a side track takes you to the summit. Key Summit (918 m) provides panoramic views of the Greenstone, Hollyford, and Eglinton Valleys, and the snowy Darran, Humboldt, Ailsa, and Livingstone Ranges. During the last ice age some 14,000 years ago, a huge glacier flowed down the Hollyford Valley where Key Summit split it to create branches into the Eglinton and Greenstone Valleys.
After a walk in light drizzly rain with little or no visibility to reach The Divide, we encountered a change in the weather. The rain stopped and gaps appeared in the clouds to allow the sun to shine through. By the time we reached the summit we were afforded snatches of views of the surrounding mountain peaks and down the Hollyford Valley. The rain recommenced as we returned the Divide Shelter.