ASPEN • In the forest along Independence Pass, there’s a place of bizarre, swirling rock and roaring water that captures the imagination of drivers who stop by.

This was a favorite place of Bob Lewis.

“Bob was an educator all his adult life,” says a longtime friend and writer, Paul Anderson, “and he brought that to bear at the Grottos.”

That’s the name of the day-use area marked along the highway close to Aspen — so named for cavernous realms cut by ancient forces and deep time.

“The Grottos tell a story of how rock and ice created the landscape of Independence Pass,” reads a sign posted at the small parking lot.

The sign is courtesy of Independence Pass Foundation, the stewarding nonprofit that Lewis created in 1989.

Lewis died in 2005 an Aspen legend. The foundation was but one environmental organization he led, among several projects following his years teaching local high schoolers biology, geology, ecology and more.

Lewis’ time in Colorado started at Camp Hale with the 10th Mountain Division. Out of the Army, outdoor education and advocacy back in Aspen would be his life’s calling. Independence Pass, that road scaling several life zones and ecosystems, would be his school away from the school building.

And perhaps there was no greater classroom than the Grottos.

“Bob would take his students up the pass and stop at intervals along the way,” Anderson says. “One of his favorite stops was the Grottos, because the Grottos revealed the ancient, formative powers that fashioned the whole pass.”

A crash course is posted by Independence Pass Foundation.

“The rocks beneath your feet are among the oldest in Colorado!” the sign remarks.

It refers to gneiss rock that formed deep within the Earth’s crust some 1.7 billion years ago. Pressure and heat pushed granite up through that older layer before another pivotal, shape-shifting era.

At the Grottos, “you, of course, see the dramatic effect of our last glacial era 10,000 years ago,” says Independence Pass Foundation Executive Director Karin Teague.

There is no more dramatic effect than the cathedral-like “ice cave,” as it is marked, for the ice known to linger in the depths for much of the year. It is one wondrous creation of glaciers that advanced and retreated here, sculpting rock along the way.

A trail continues above, over a granite humpback and on to the feature marked as “the cascades.” The Roaring Fork River charges through the ornately curving rock. The water is deafening, its effect equally astonishing and refreshing for onlookers who carefully roam beside it.

Lewis was one of those onlookers.

“Bob would’ve been in awe of the time and space that the Grottos represented,” Anderson says. “From the Cretaceous seaway to the mountain peaks we see today, he would’ve been able to grasp that time frame by walking across those glacial striations.”

Such is the feeling of knowledgeable locals today, including Anderson. “Longtime Aspenites know the Grottos as, I would say, almost a sacred place,” he says.

While everything changes around town, “to know there is constancy in the natural world, I think that is sort of soothing and comforting,” Anderson explains. “You can walk the same trail you’ve walked and perch on a granite outcrop and feel that force of the Roaring Fork River. There’s something about that consistency that is soothing.”

And yet the landscape is changing. Compared with Lewis’ day, “certainly a lot more people come over the pass now,” Anderson says.

They popularly stop at the Grottos — “a great place to get out and stretch your legs and take a break,” says David Boyd, public affairs officer for White River National Forest.

The Grottos Day Use Area is an unsuspecting stop for some, a go-to, riverside picnic spot for others.

It’s a scenic destination of its own for others drawn by fantastical images seen on social media. “Social media has certainly added to the popularity of specific sites like this,” Boyd says.

The site sees up to 200 people a day, he says. The parking lot is often full; Boyd encourages a plan B for drivers.

Up the road is the Braille and Discovery trails — creations of Lewis going back to the ‘60s. The Braille Trail is defined by stations linked by a cord, held by visually impaired people who stop to touch the copper messages. Lewis went on to design the Discovery Trail for people in wheelchairs.

Those trails would be for all, Lewis imagined, while the Grottos posed more hazards.

“It takes a little bit of dexterity and just awareness of the rock,” Teague says. It’s a steep, slick descent into the ice cave, she notes, while the rock around the nearby waterfall should also be met with caution.

But more than anything, “the Grottos are super-peaceful,” Teague says. “It’s just really a place where you can feel a real intimacy with the natural world and really appreciate that.”

That’s what Lewis wanted — he wanted more people to feel that. More people means the organization he founded is picking up more trash and conducting more trail maintenance.

Maybe Lewis could not have foreseen such crowds. But his old friend thinks he would be pleased.

“I think Bob would’ve been thrilled to know that people are gravitating to the Grottos and sharing the enthusiasm that he had,” Anderson says.

It was an enthusiasm for nature, for the lessons it can teach and the humility it can inspire — if we care to stop and respect it.

Lewis “quoted Leopold a lot,” Anderson says. “In order to save something, you must love it, and in order to love it, you have to know it and understand it.”