I’m whizzing through the air along a metal wire suspended over a gorge. All around me is lush greenery, jungle spilling down the sides of the valley. To my left a bare rock face, water cascading over the edge to form a huge waterfall, a rainbow down at the bottom where the sunlight hits the spray off the rocks. The speed is exhilarating and I shriek with joy, drowning out both the whining wirr of the zip line and the rush of the waterfall.