The top of the Grimsel is a bare, grey bowl at 2,164 metres where the Bernese Oberland hands over to the Valais, and the first thing you notice is how little grows here. Granite polished by ice, a few tarns, and the small dark Totesee, the Dead Lake, lying beside the road as if someone had set down a slab of slate. Meiringen is the nearest proper town, a good twenty kilometres of road behind you, and Andermatt is about the same distance the other way.
The approach from the west is one of the great climbs for a motorbike. You leave the Aare valley at Innertkirchen and work up past the reservoirs of the Oberhasli power company, where the water is that unreal milky green, and the hairpins stack up on the last rise to the pass. The surface is good, the bends are wide enough to find a rhythm, and in the early morning there is almost nobody on it. By eleven on a summer Saturday you will be sharing it with every sports car and coach in central Switzerland, so leave early or accept the company.
This is a watershed in the plain sense: rain falling on one side ends up in the North Sea via the Aare and the Rhine, and on the other the Rhone carries it to the Mediterranean. The old mule track over the Grimsel was a trade and pilgrim route for centuries, and the hospice at the western foot was a famous stop long before the road. Walkers still cross by the old paths. Marmots whistle from the scree below the road, and with luck you will see ibex higher up on the crags.
A little restaurant is usually open near the top in season for coffee and a heavy slice of something. The pass is shut by snow from late autumn into early summer, and even in July the wind up here can turn raw within minutes, so keep a warm layer in the bag. Take five minutes at the Totesee before you drop down towards the Rhone glacier.