Steep cliffs and glacier-covered mountains flank this fjord, fringed by the largest intact coastal temperate rain forest in the United States. Old-growth trees colonized Tracy Arm’s mouth long ago as the Ice Age retreated. But further up the sinuous 48-kilometer (30-mile) waterway, its icy grip lingers a little. There, the twin Sawyer Glaciers flow from the peaks down to the sea, sloughing off stories-high chunks of water frozen decades or even centuries before. Even more glorious than nearby Glacier Bay, Tracy Arm is part of the 5.7 million acres (or around 23,000 square kilometers) of pure wilderness sheltered by the Tongass National Forest (America’s biggest). Visitors often see bears, whales and mountain goats roaming across various corners of this pristine area—not to mention chubby baby seals resting on the ice floes.Summer temperatures average 35 to 60 degrees Fahrenheit (0 to 16 degrees Celsius), so pack warm clothing. And don’t forget waterproof gear, even when traveling by cruise ship: More than a meter and a half of rain falls here each year! We also recommend a water bottle, thermos or reusable coffee cup: On scenic cruising days, cruise ships ban paper and disposable plastic products that could litter this unsullied environment.