Frosted crags descend into mossy forests and a 457-meter-deep (1,500-foot-deep) fjord at this World Heritage Site, which is also one of the planet’s largest biosphere reserves. Stone, ice and water continue to collide, sculpting a dramatic landscape that is the crown jewel of southeastern Alaska’s natural wonders.

The area’s first European explorer missed it all—but with good reason. When Captain George Vancouver sailed here in 1794, a vast shield of ice, more than 1,200 meters (3,937 feet) thick, dominated the area. In one of the fastest retreats on record, the glaciers shrank back 105 kilometers (65 miles) by 1916. The formerly glacier-squashed land is rebounding now, rising 30 millimeters (1.18 inches) each year. Visitors can observe this rebirth: A spruce-hemlock rain forest has sprouted near the mouth of Glacier Bay. Farther north, the more recently exposed land shows sharper edges and thinner vegetation. Still, it’s enough to encourage the return of wildlife, from bald eagles to bears, moose and humpback whales.

While the national park is open year round, most travelers prefer the warmth of late May to early September. Even in summer, be prepared for any weather—especially rain! Pack a hat, gloves, wool or fleece layers, a warm coat and waterproof gear if you want to admire the landscape from the open deck of your ship.