United States

The United States is less a destination than a continent's worth of them, and the single most common planning error is to underestimate the distances — New York to Los Angeles is a longer flight than London to Cairo. The first useful question is which America the trip is actually about.

The cities each argue their own case: New York above all, but also the coastal trio of San Francisco, Seattle and Portland, and the distinct cultures of the South. The other America is the one held in the national parks — Yosemite and the Grand Canyon, Yellowstone's geysers, the red-rock country of Utah — a public-lands system that remains one of the country's genuine wonders. New England in autumn, the California coast road, the Pacific Northwest's forests: each is a trip on its own.

For a country this large, no single season fits all of it. May, June, September and October are the broad sweet spot — warm enough for the parks, clear of the high-summer crowds and heat, and timed for the autumn colour in the north-east.