IN BAD visibility it is easy to become disoriented. Trees not only remind you which way is up, but also break up omnidirectional light and throw into relief the variations in the surface of the snow. And, whatever the weather, trees give pistes a definition they otherwise lack.

Most of the 'serious' skiing in the Alps is above the trees; in the American Rockies the opposite is true and Vail, one of the resorts vying for the 'biggest in the US' label, has quantities of woodland skiing that are unmatched in Europe.

PLUS POINTS: Big, varied ski area, including extensive off-piste back bowls; usually good snow conditions, with Colorado's famously dry powder; cute Alpine-style village, traffic-free in the centre for much of the day; customer-oriented resort, with friendly people and efficient infrastructure; impressive accommodation; wide range of apres- ski; smart shopping.

MINUS POINTS: Lack of scenic drama; limited choice of mountain restaurants; relatively expensive - one of the US's smartest resorts.

Photograph: SKISHOOT

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