Recently I embarked on a journey into the Serengeti. It wasn’t the Serengeti you might envision, not the postcard vistas of rolling, yellow-grass savannas punctuated by umbrella thorn acacias. And I didn’t stay in a luxury tented camp or join the armies of tourist vans swarming around lion kills.

Instead, I traveled to Loita, a part of the greater Serengeti ecosystem that doesn’t appear on the standard itinerary—a hidden Serengeti, if you will, one that includes a lush mountain wilderness rising more than a mile above sea level. It’s about a 150-mile drive southwest from Nairobi and overlooks the world-famous Masai Mara National Reserve. Yet it’s a place most visitors to Kenya don’t know exists.

My plan was to make my way up into the heart of this green fortress to a place known in the Maa language as Entim e Naimina Enkiyio, or the Forest of the Lost Child. It’s a 115-square-mile cocoon of unspoiled rainforest, a land practically hidden in plain sight. Once there, I hoped to be granted an audience with the man who oversees this realm.