With its steep ups-and-downs and unstable scree fields, the 24 day Inner Dolpo trek is one of the toughest in Nepal. The first half of the trek traces the footsteps of writer Peter Matthiessen and naturalist George Schaller, who explored the region in 1973 to study the rare Himalayan blue sheep and its main predator, the snow leopard. The book The Snow Leopard has lured many a trekker and adventurer to Nepal. But not many dear to venture on the long hard trek to Dolpo. Relatively untouched, it remains a purely Tibetan (by culture and nature) enclave north of the Himalaya range.