This photo was shot with a circular polarizing filter on the front of the lens. It darkens the sky by filtering out the scattered light from dust and haze. This leaves a very high-contrast result, with very nice detail on distant subjects (such as any mountains that happen to be around).
Here’s another view of the scene, this one only partly improved by the use of a polarizer. Notice that the view is more natural looking; the one bad thing about a polarizer is that it imparts an artificial feeling to the photo.
I can’t say I favor one approach over another; any photograph of Rainier on a clear day makes me happy.
Both photos were taken with the Sony a1 with the Zeiss Otus 100mm f/1.4 lens. The top photo is a horizontal panorama, made of five shots combined. Shots taken with the camera held vertical. The lower photo is a vertical panorama, with the camera held normally (horizontal) and three shots combined.
Astounding clarity.