The villages we'd be stopping in would all be 7 to 10 miles apart on a path that follows a steady gradient up a single valley, a positively leisurely prospect compared with the up-and-down slogs from one valley to the next that characterize many Himalayan trails.

WSJ: Trekking the Har Ki Doon Trail in India's Himalayas

For the ultimate show-stopping view, stand at the harbour edge in Tsim Sha Tsui and take in Hong Kong Island's skyscrapers' gradient-defying march up steep jungle slopes.

BBC: The amazing views of Hong Kong

Pushed for time and strapped for cash, the engineers laid eight miles of track straight up Big Hill, at a gradient more than twice the safe maximum.

BBC: The wonders of Canada by rail