SISTERS, Ore. (AP) — As first-time climber Adam Rosalez stood in the shadow of Oregon’s third-tallest mountain on a perfect September morning, he couldn’t help but wonder exactly what he was getting into.

The 29-year-old Minnesotan’s only experience with mountains involved riding a chairlift up them or admiring them from a distance, and the number of trails he’d hiked could be measured on one hand.

Yet here he was, about to ascend into the thin air of South Sister, a 10,358-foot volcano that stands above Central Oregon like a gigantic ice-cream cone.

“So . exactly how hard is this going to be?” he asked.

Four hours later, after a grueling climb of more than 5,000 feet, through a treeless desert of pumice and snowfields that exist year-round, he would have his answer while sitting atop what might be Oregon’s most spectacular view.

From the summit, Middle and North Sister rise so close it feels as though all it would take would be a good jump to land on the tops of the two 10,000-foot volcanoes. Beyond, the string of Cascades including Jefferson, Hood, St. Helens and Adams stood out like snow-capped islands in the sky.

“That was one of the hardest things I’ve ever done in my life, but also the most rewarding” Rosalez said. “This is the first time that I’ve really been able to grasp what it feels like to be on a mountain. It’s an amazing experience.”

It’s a common feeling for those who climb this peak. Known as the perfect summit for first-time mountaineers, South Sister has inspired a generation of climbers who become life-long enthusiasts (some even become celebrities in the process).

But the same things that make it so appealing to the average Joe also make it perilous.

South Sister is not an easy summit by any measure.

From the Devils Lake Trailhead, about 30 miles west of Bend, the 11.6-mile round-trip journey climbs a whopping 5,083 feet. Even those in good shape will have legs of cement by the day’s end.

What sets this mountain apart is the trail that climbs all the way to the summit. In contrast to many of Oregon’s tallest mountains, which require routefinding or technical equipment and knowledge, South Sister only requires the ability to put one foot in front of the other many, many times.

The trail is typically free of snow by August and September. An ice-axe and crampons aren’t needed during this part of the season.

The easier nature of the climb does pose some problems. Many people on the trail have little experience with the thin air above 9,000 or 10,000 feet.

Even more dangerous is what can happen if a storm blows through. Do not climb in crummy, or even potentially crummy, conditions. Weather that seems halfway decent at the trailhead is almost certainly worse at 10,000 feet.

The best advice? Start early, check conditions, take your time and bring plenty of water and snacks.

The climb up South Sister isn’t just about reaching the top.

With the exception of the first 1.5 miles of forested trail, the hike showcases so many beautiful views that tripping over amateur photographers snapping photos is a hazard.

The plateau at mile 1.7 features South Sister in all its glory. A trail on the right takes hikers down to beautiful Moraine Lake, emerald green with views of Broken Top in the distance.

After mile 3, the trail starts to shoot uphill with a vengeance, climbing 1,800 feet in 1.5 miles to an overlook that from below fools many into thinking it’s the summit.

Not so, but this flat plateau does feature a milky green lake from snowmelt off Lewis Glacier and a view of the final push up a reddish scree slope to the summit.

The final stretch is 1 mile and 1,330 feet to the summit ridge, followed by a celebratory half-mile stroll around the volcano rim, past Teardrop Pool, Oregon’s highest lake, to the actual summit.

Make sure to take some time enjoying the summit before heading down. Most people take around eight hours to complete the climb.

I’ve written about it more than once, but crowds are a serious issue here.

On bluebird weekend days in September — and even mid-week — the trail can feel like a shopping mall escalator.

A sunny weekend day in August and September can see upwards of 400 people attempting to climb South Sister at once.

“You’ll find less people out there on a Wednesday, but to be frank, there really isn’t a way to avoid a busy setting,” said Jonathan Erickson, lead wilderness ranger for Deschutes National Forest.

The experience of climbing South Sister is often enough to get people who never expected to become mountaineers into the sport.

One famous example is Corvallis native Jon Krakauer, author of bestselling books “Into the Wild” and “Into Thin Air,” who took his first trip up South Sister when he was 8 years old. That trip would spark the author to become a self-proclaimed “climbing bum” and eventually the pre-eminent adventure writer of the last 25 years.

A more local, and more common story, is that of Gates couple Cathy Lazarus and Stephen Rockford. Already in their 50s, a friend took the couple up South Sister. They loved it so much they joined local outdoor club The Chemeketans and proceeded to climb 45 mountains in just three and a half years.

“We had so much fun,” Lazarus said in a February 2013 interview with the Statesman Journal. “Right away we were sold. We wanted to keep doing more.”

After his first climb, Rosalez had a similar reaction.

“Man, I want to do that again!” he said.