The morning air tastes of dust and eucalyptus as the convoy leaves Nairobi, the city shrinking behind you and the Rift Valley widening like a promise. By mid-morning the canopy of Kereita Forest folds overhead: a room of trunks and ferns where birds choreograph the light. Here—halfway between cultivated farms and the raw escarpment—you clip into a harness and run a palm over the zipline’s steel cable. For a few seconds the forest exhales beneath you, and East Africa’s longest zipline sends you skimming above gullies and waterfalls with the valley laid out in steps below.