The Chyulu Hills sit between Tsavo and Amboseli, a young volcanic range of rolling green cones that Ernest Hemingway wrote about and that still sees a fraction of the visitors either neighbouring park gets. This is the one hiking-led trip in the catalogue: two days of walking the ridgelines and cave systems (including access toward the Leviathan lava tube, among the longest in the world) with a fly-camp moved along the route each night. Views run to Kilimanjaro on one side and Tsavo’s plains on the other. It’s rated challenging not for technical difficulty but for sustained walking at altitude across several hours a day, genuine trekking rather than a game-drive-with-a-stroll.