Not particularly high altitude, but when I was a university student in the early 90's me and a girlfriend went on an impromptu camping trip in the Lake District. We didn't know the area too well, but we were near Eskdale and wanted to get across to Ambleside for the night.
The maps showed a direct route through the valley, which gradually got steeper and steeper... which we later discovered were Hardknott and Wrynose passes at 1-in-3 inclines. We were two-up in a Mk4 Mini with a Metro 998 HLE engine which to be honest was rather tired and lacking compression (typical student transport, patched together from random bits).
On the worst of the hairpin corners she got out and hiked, while I took several run-ups and slipping the clutch to get the car up and around the bends - much to amusement of a Land Rover driver coming down the opposite direction. Fortunately the car had 1275 GT discs on it, so brake fade at least wasn't a problem on the way down
