You step out into the Nairobi morning and the city’s traffic thins quickly into open sky. Within an hour the car is coasting along the rim of the Great Rift Valley — the road a ribbon cut into volcanic slopes — and the air sharpens. On day one the landscape loosens its grip on the urban grid: red earth, gullied escarpments and the first suggestion of a lake shimmering below. At Hell’s Gate the trucks are left behind and cyclists mount sturdy mountain bikes for two hours of trail riding among cliffs and scrub. Rock faces, warmed by the sun, seem to lean in as you pass the narrow gorge mouths; the breeze off Lake Naivasha cools your neck and mornings are full of bird calls that dart like punctuation marks.