As other cruise ships head for the Caribbean in late autumn, Marco Polo, the Grande Dame of the Baltic, keeps her cool up north, and that's just how her passengers like it. They've paid to see Old World cities such as Copenhagen, St. Petersburg and Helsinki without crowds of tourists, but traveling this time of year is a risky venture. And while this 50-year-old liner is built to plow through broken ice on arctic routes, a new captain, some unpredictable seas, and a brooding hurricane will make this a historic ride in more ways than one.