“Just keep walking,” my brother, Jared, yelled from farther up, where the track widened. “It’s easier if you go fast.” Jared and I had spent the past six days adventuring through Corsica, a French ...

I clung to the face of the limestone cliff like a crab, my fingers turning white as they clawed the chalky rock. To my left, the sandy path where I stood narrowed, dropping away more than 200 feet ...