Lusaka in 3 days: the world's youngest-median-age capital (median age 17), where 70% of national earnings come from copper, where orphaned elephant calves drink 22 litres of special formula daily, where the Kafue National Park (third-largest in Africa) is 2 hours west, and where the 'Smoke that Thunders' — the largest waterfall on earth — is 1 hour by plane to the south.