The same verticality that draws skiers in the winter lures the nubby-tires set in summer. The 20 or so trails are rated in difficulty the same way ski runs are (green to black), so you don't have to be an expert to relish the gravity-fed thrills. From seven-mile Village Trail, a meandering green, to '94 Downhill, a technical romp used in the 1994 World Cup Mountain Bike races, most trails are reachable by the Eagle Bahn gondola. Adventure Ridge, an activity center at the gondola's drop-off point, rents full- and front-suspension bikes (970-476-9090; www.vailsummer.net).

With 5,289 skiable acres and 33 lifts, Vail is enormous. Getting your bearings on the slopes can take days, but you'll never get bored cruising the range of glades, bowls, and wide-open groomers. Even better, the snow is pristine Rocky Mountain powder that averages 350 inches a year—forget about those ice chutes they call runs on the East Coast. Vail's Front Side, which rises up from the village, offers a good mix of terrain, including double-black diamonds off the old Highline chair to the west (Roger's Run and Blue Ox are two favorites), and easygoing groomers off the Avanti Express to the east. But to get the full value from your lift ticket (more expensive every year), frolic in Vail's incomparable Back Bowls, accessed mid-mountain over the Patrol Headquarters peak from either the Mountaintop Express chair or the Northwoods Express (follow signs to Sun Up Bowl or China Bowl). Sparsely groomed, but beautiful and wide open, they're perfect for advanced skiers. Just past the bowls you'll find epic Blue Sky Basin (accessed from a catwalk trail off Sun Up Bowl), where spruce and fir trees are scattered amid 645 acres of ungroomed powdery bliss. This is territory for the quite advanced skier and boarder, but cliff-huckers and cruisers alike can spend the entire day exploring Blue Sky. Tip: Head there first thing in the morning, because it takes 45 minutes to reach from the village and Blue Sky starts shutting down in the early afternoon. Snowboarders who go for tricks are kept happy with four terrain parks, a 400-foot-long Superpipe (picture a half-pipe on steroids), and manmade obstacles such as rail slides on Front Side (970-476-9090; vail.snow.com).

Beaver Creek is decidedly smaller than Vail, with 1,805 skiable acres and 16 lifts, which is why so many skiers and boarders love it. It gets the same average snowfall, but is much easier to navigate: You can get your bearings the first day, yet it is still big enough, with its village-to-village skiing, that you can try something new each day. The new Stone Creek Chutes on the western edge and Talons Challenge terrain (mid-mountain, centered around Grouse peak) should satisfy any expert. There are also three freestyle terrain parks suitable for all levels, including a super pipe.

Ski and board rental: Equipment can either complement your day or completely wreck it. Whenever possible, "demo" skis rather than renting them—this is a gimmick in which the ski shop is hoping you'll actually buy those type of skis, and they're almost always better equipment than rental gear. In Vail, the American Ski Exchange, next to the Vista Bahn Express, demos Salomon, K2, Rossignol, Völkl, Volant, and Head skis (225 Wall St.; 800-327-1137; vailskishop.com). In Lionshead Village, Double Diamond demos everything it sells, so opt for a Demo Package (877-433-7547; www.doublediamondvail.com). One Track Mind, in Lionshead Village, specializes in snowboards (970-476-1397).

In Beaver Creek, Beaver Creek Sports, with equipment both for sale and rent, has locations at every base chairlift, including one inside the Ritz-Carlton. You can also reserve your equipment before you arrive (970-845-5418;. www.beavercreeksports.com).

There's no better perspective on the mountains than from the top of one: The bonus at a ski resort is the ability to save yourself a five-hour uphill hike to achieve that 360-degree view. The Eagle Bahn gondola offers free scenic rides from 2 p.m. to 9 p.m. (Tues.– Sat.) in the winter. It also runs during the summer months (free Thurs.–Sat.), linking up to a warren of hiking and mountain-biking trails.