NO wonder Vancouver is often heralded as one of the worlds most livable cities. It is blessed with a snowcapped mountain backdrop and crystal blue harbors. It is also a gateway to the Inside Passage the marvelous maze of glacier-carved fjords and forested islands that are a cruise lovers delight. But what really sets Vancouver apart is its urban density. With sprawl kept in check by geography, the city thinks vertically. Neighborhoods overlap, apartments rise. That seems to heighten the citys international mix, and not just when the Olympic Games are in town.