Hiking through a microcosm of Earth

About 3,000 vertical feet - that is all it takes in New Zealand to go from rolling greenery to exposed rock ridges where it is too cold and windblown for most grasses, much less trees, to grow. Due to the country's location in the Roaring Forties latitudes, 3,000 vertical feet is much more extreme than the same altitude ascent in a milder climate. The Avalanche Peak hike is perhaps the most dramatic way to experience this phenomenon, as it climbs this height, and descends it again, in a stretch of only 4.5 miles. Climbing Avalanche Peak (6,013 ft) feels like hiking out of the Grand Canyon, only the shifting strata are plants, not rock. At first the trees are big and burly, covered in a thick red moss. Then the trees begin to shrink and hunch, like old men, beards of pale green lichen hanging from their limbs. Next the trees disappear altogether, leaving only the hardy clumps of tussock grass on the hillside. Finally, these too fall aside, and it is just you and the sharp black rock as you make their way along the ridge to the summit, snow-capped peaks gathering round to welcome you into their domain.  Well, just you, the rock and those cheeky keas, New Zealand's alpine parrot. First they make you laugh, then they steal your lunch. You have been warned.

Ancient forests and deep fiords
Fiordland National Park
Best known tracks: Kepler Track, Routeburn Track, Milford Track

Although Fiordland has several celebrated walks, the Kepler Track is probably the easiest to navigate, as it begins and ends in a town, requiring no extra transport. Hikers travel from the shores of Lake Te Anau to the shores of Lake Manapouri via a full-day tramp along an exposed ridge, looking down on the park's namesake fiords. It is hard for those who regularly lust after alpine scenery to contemplate, but the last two days - flat trekking through forest - are probably the tramp's highlight.

It feels like you are walking through a painting. Fiordland's forests are predominantly made up of beech trees, whose tiny, regular leaves dot the canopy with small, delicate brushstrokes. With more than 20 feet of rain a year, these forests are as wet - and correspondingly lush - as a tropical rainforest. Ferns carpet the forest floor while moss carpets the trees; rarely is a patch of trunk visible. The path itself, tan and loamy from the millions of fallen beech leaves, feels like it is chalked in, like Dick Van Dyke's magical paths in Mary Poppins. The last night comes along the shores of Lake Manapouri, where the waters are as warm as any lake on the South Island, just begging to cool your legs.

Clarification: A previous version of this article stated that the Serengeti was in Kenya. The Serengeti region encompasses the Serengeti National Park itself, the Ngorongoro Conservation Area, Maswa Game Reserve, the Loliondo, Grumeti and Ikorongo Controlled Areas and the Maasai Mara National Reserve in Kenya.