This trip starts with a bang: a 4.4-mile, 2,874-foot climb from Bear Lake trailhead to 12,324-foot Flattop Mountain. Head northwest on Tonahutu Creek Trail 3.5 miles across Bighorn Flats; end just below treeline at Renegade campsite.

The next day, stroll downhill 4.5 miles to Big Meadows and camp in .75 to 1.5 miles at South Meadows or Paintbrush campsites. From here, it's less than two hours to the village of Grand Lake. Follow Summerland Park and West Portal Roads for 1.5 miles to East Inlet trailhead. Walk up the East Inlet drainage 6.6 miles to Lake Verna for the best campsite in the valley. Take a rest day and explore the emerald-grass shores of Fifth Lake, below aptly named Isolation Peak (13,118 feet). To reach Boulder-Grand Pass, follow an unmaintained trail east, past Spirit Lake, to the north side of Fourth Lake. Bushwhack steeply to the east-northeast to the 12,061-foot pass. Descend the east side, skirting a permanent snowfield alongside a steep gully on the left (north). Continue to the designated campsite just east of the patrol cabin beside Thunder Lake.

On day six, climb northeast through open forest to the Lion Lake Trail. After a .5-mile side trip to explore the wildflowers around the Lion Lakes and Trio Falls, follow game trails east from Lion Lake No. 1, climbing about 500 vertical feet to North Ridge, just west of Mt. Orton. Contour down the far side to the north and camp at the upper end of the Hunters Creek cross-country zone.

Next morning, climb to the cirque below Longs Peak's south face. Keplingers Couloir rises steeply for 1,600 feet to the Notch, between Longs and Mt. Meeker. A few simple hand-and-foot moves are required to pass obstacles; keep right when in doubt until you reach the base of the Palisades cliffs. Expect snow in this chute until late June. Traverse left across exposed slabs to the Keyhole Route; follow red-and-yellow blazes to the cleaved summit of Longs Peak (14,259 ft.). Finish an exhausting day with a 10-mile, 4,800-foot descent of the Keyhole Route, North Longs Peak Trail, and Glacier Gorge Trail to close this 43-mile loop.

WHEN TO GO: Wildflowers explode in mid-July; elk bugle in September. Check conditions on Longs' upper faces before starting—snow and ice may require technical skills (plus an ice axe and crampons) in shoulder seasons.

PERMITS: Reserve permits ($20 per trip) by phone starting March 1; after May 15, mail in requests or apply in person at the backcountry office beside the Beaver Meadows visitor center: nps.gov/romo, (970) 586-1242; Backcountry Office, Estes Park, CO 80517. Permitted backcountry camping is limited to seven consecutive nights per party.

VACATION PLANNER: Get hotel, restaurant, and great travel beta at nationalparktrips.com/rockymountainpark.aspx

3D VIDEO: See video clips and fly this route in 3D at www.backpacker.com/3d_flyover_rocky_mountain_national_park/videos/89

-Mapped by Dougald MacDonald

PLAN IT
MAP
Rocky Mountain National Park ($12, natgeomaps.com)
Order USGS topo quads at store.usgs.gov.
Order a custom map of this route using MyTopo.com

CONDITIONS
Trail Ridge Road is closed from November to April. Check conditions for the east side of the park check Estes Park, CO (80517) Weather

PERMIT 
$20 for entry to Rocky Mountain National Park; (970) 586-1242, nps.gov/romo

ROCKY MOUNTAIN NATIONAL PARK INFO
Visitor Information (970) 586-1206 (daily, 8 a.m. to 4:30 p.m. Mountain Time; recorded information after hours)
Trail Ridge Road Information Recorded Message 970-586-1222 (available 24 hours a day, updated when conditions and/or road status change)
Visitor Information for the Hearing Impaired (TTY): 970-586-1319 (daily, 8 a.m. to 5 p.m. Mountain Time)
Backcountry Office (970) 586-1242

OTHER RESOURCES
GAS
Shell‎ 860 Moraine Ave. Estes Park, CO (970) 586-7867
GEAR
Grab supplies or gear rentals (packs, bags, pads, and fishing gear) at Estes Park Mountain Shop, 2050 Big Thompson Ave., Estes Park, CO; (866) 303-6548.
GROCERIES
The Country Market National Park Village 900 Moraine Ave. Estes Park, Colorado (970) 586-2702
RESTAURANTS
Try a Mountain Mai Tai and the buffalo-and-bacon meatloaf at Peak-to-Peak American Grille, 451 South Saint Vrain Ave., Estes Park, CO; (970) 577-0577