An African safari might strain the budget this year, so why not an American one? Yellowstone's two-million-plus acres lie at the heart of the largest intact ecosystem in the continental U.S. Herds of bison graze in the valleys. Bighorn sheep clatter across the slopes of the Absarokas. And in the wilds of Lamar Valley, wolves are again slipping in and out of the shadows. For any visitor with a pair of binoculars, all this can translate into some heart-pounding wildlife encounters. In Yellowstone, humans are as much a part of the play as the animals.

Photo Gallery: View stunning photos of Yellowstone National Park in National Geographic's Parks Guide here.

GAME PLAN: Yellowstone is laced with a huge network of paved roads, some 310 miles in all, many of which make for perfect DIY game drives. Start with the route from Mammoth, Wyoming, to Cooke City, Montana, along the park's northern edge. In the open meadows that line the road you may spot black bears, grizzlies, or coyotes, while in Lamar Valley you may glimpse a wolf (if you are very, very lucky). Keep an eye out for parked cars and folks with spotting scopes, sure signs that some action is afoot. In the afternoon, plan short hikes up the Trout Lake, Pebble Creek, and Slough Creek Trails. After a day or two up north, turn your sights south to the route from Tower to the northern edge of Yellowstone Lake. Stop off at Grizzly Overlook to glass the Yellowstone River for ospreys and bald eagles, then continue south that afternoon to hike either the Pelican Creek Nature Trail (great for bison) or the slightly longer Pelican Creek Trail (the best griz habitat in the park).

Vitals: To hedge your chance of seeing wildlife, consider going guided. Yellowstone Safari runs four-day, three-night trips that track the recent movements of animals ($1,600 per person, including meals and lodging; yellowstonesafari.com). The Yellowstone Association offers three-day Wolf and Elk Discovery programs ($619 per person, including lodging and most meals; yellowstoneassociation.org).

The Must-Do: Not to talk anyone out of jostling for a look at Old Faithful, but the 3.2-mile hike up Mount Washburn (10,243 feet) gives you all of Yellowstone—views of forests, geyser basins, subalpine meadows, and the sprawling Hayden Valley—in the company of about 5,000 fewer people.

Base Camp: Built from 1903 to 1904, the Old Faithful Inn gave birth to the concept of "parkitecture"—the notion that park lodges should be big, grand, and bear the spirit of their surroundings. To wit, the inn features massive timbers, a 76-foot-tall stone fireplace, and a killer setting beside its namesake geyser (doubles from $93; travelyellowstone.com).