No adjectives can do justice to Rocky Mountain National Park. The jagged peaks, rocky tundra, green valleys and roaring waterfalls render exclamation points inadequate.

The beauty is almost unearthly, and autumn is one of the better times to experience it. Aspen trees turn brilliant yellow; the bugle-
like mating calls of elk echo in the mountains. And starting this month, Rocky Mountain National Park launches a year of festivities to celebrate its centennial, including special hikes, wildlife seminars, art shows and a wild game culinary fest.

The eastern side

The Continental Divide runs through the park, and the western side is greener and rainier, known as the “wetter, better side,” with more moose and bears – though a ranger told us only two dozen bears live in the park. The eastern side, while more crowded, is barely more than a two-hour drive from Colorado Springs.

The park has five campgrounds, with two open year-round, but my hiker pal and I stayed in a low-key motel-lodge at the town’s edge, with an indoor pool and hot tub to soak tired feet after a day on the trail. It was a short drive from there to several trailheads, some best accessed by free park shuttle buses since parking lots often fill.

Planning the hikes

Start at a park visitor center to get maps and rangers’ advice on terrain, difficulty and distance. Some trails are even accessible to strollers and wheelchairs.

But remember this mantra in the high mountains: It’s not the distance, it’s the altitude. Many hikes climb above timber line, which is at roughly 11,000 feet in the park. Altitude sickness – which can include dizziness, headaches, fatigue and disorientation – can occur several thousand feet below that.

Water is key: Bring plenty and drink often to avoid dehydration in the arid mountain air.

Bear Lake corridor trails

This system of trails south of U.S. 36 is only a few minutes from Estes Park. A park-and-ride shuttle lot is near the Bear Lake trailhead. We chose a roughly 6-mile route, steep and gravelly in spots, past serene Nymph Lake, covered in lily pads, and up past Lake Haiyaha – a must-see climb over huge boulders to glimpse a gorgeous blue-green alpine lake surrounded by snow-capped peaks. We circled round past the turnoff to Mills Lake, with views of more peaks through forests of spruce, fir and quaking aspens, along with the dramatic Alberta Falls waterfall, back to the trailhead.

Upper Ute Trail

Even if you don’t make the entire 8-mile round trip on the Upper Ute Trail, from the Alpine Visitor Center to Milner Pass and back, you’ll still see awe-inspiring dramatic scenery, from barren tundra to alpine meadows and ponds, with stunning views of 14,255-foot Longs Peak. While this is fairly easy terrain, beware of weather and high altitude. The trail starts at about 11,780 feet and you’ll be the tallest thing around on the barren first portion. Know the forecast – a must in the mountains but especially where you’re so exposed. The park’s first lightning deaths in more than a decade occurred on or near this trail this summer. Darkening clouds and my hiking partner’s altitude sickness made us turn back before the pass.

President Barack Obama addresses the nation from the Cross Hall in the White House in Washington, Wednesday, Sept. 10, 2014. In a major reversal, Obama ordered the United States into a broad military campaign to “degrade and ultimately destroy” militants in two volatile Middle East nations, authorizing airstrikes inside Syria for the first time, as well as an expansion of strikes in Iraq. (AP Photo/Saul Loeb, Pool)

Saul Loeb

This July 20, 2014 photo shows a portion of the Upper Ute Trail in Rocky Mountain National Park in Colorado, one of several good day hikes in the eastern side of the park, using the town of Estes Park as a gateway. The park is launching a yearlong celebration of its centennial in September, and fall is a nice time to visit. (AP Photo/Lindsey Tanner)

Lindsey Tanner

This July 20, 2014 photo shows an elevation sign post a short hike up from the Alpine Visitor Center on the edge of the eastern side of Rocky Mountain National Park in Colorado. There are several good day hikes in this region of the park, using the town of Estes Park as a gateway. The park is launching a yearlong celebration of its centennial in September, and fall is a nice time to visit. (AP Photo/Lindsey Tanner)

Lindsey Tanner

CORRECTS LOCATION NAME FROM NYMPH LAKE TO ALBERTA FALLS – This July 19, 2014 photo shows Alberta Falls in the Bear Lake Corridor Trails area in Rocky Mountain National Park in Colorado. The corridor offers good day hikes in the eastern side of the park, using the town of Estes Park as a gateway. The park is launching a yearlong celebration of its centennial in September, and fall is a nice time to visit. (AP Photo/Lindsey Tanner)

Lindsey Tanner