When Katherine Choong suggested to her friend Éline Le Menestrel that they tackle the Zahir, a classic route in the Swiss Alps and a demanding gem of the Wendenstöcke, Éline agreed... on one condition: that they only use sustainable transport to get to the foot of the wall. As the days passed suspended on the rock, they realized the scale of the challenge: intense commitment, tiny holds, accumulated fatigue from cycling... every movement became a challenge. Between motivation and euphoria, per...