When I read the pop-philosophy novel “The Fountainhead” at 19, I wanted the main character — architect Howard Roark — to be real. An idealistic youth, I was enchanted by author Ayn Rand’s ideas. Her obsession with self-determination worked my cognitive skills, as her devotion to authentic art and architecture touched my spirit.

And then I learned about Frank Lloyd Wright, the famous American architect from whom Rand had drawn inspiration for the 1943 tome.

Like the fictional architect, Wright envisioned purpose-built structures being of and for the setting and owners. He called this quest for harmonious design “organic architecture.”

Throughout his life he articulated that philosophy in words and buildings.

“No house should ever be on a hill or on anything. It should be of the hill. Belonging to it. Hill and house should live together each the happier for the other,” he espoused.

Fallingwater — the iconic country retreat Wright created in the 1930s for the Kaufmanns of Pittsburgh is “organic architecture” incarnate. Straddling Bear Run Creek with sandstone boulders rising from the floor to create a fireplace hearth in the main living area, it integrates nature instead of observing it.

Despite my fascination with Wright’s fresh vision of the built world, it took me nearly 30 years to make the three-hour drive from my home in Northeast Ohio. About 90 minutes southeast of Pittsburgh, Fallingwater is the only major Wright-designed house open to the public with original furnishings and artwork.

The drive was worth it. One can’t understand the aesthetics without hearing the birds and water and seeing subtle shifts of light and shadow.

While you don’t have to read “The Fountainhead” or architectural texts to appreciate buildings in harmony with man and environment, some background will help you experience the standard 90-minute tour of the iconic 5,330 square feet of concrete, steel and glass rooms and terraces. Longer specialty tours are available for an upcharge.

In the 1930s, Pittsburgh was a steel manufacturing center that suffered dark, polluted skies. Those with time and money escaped to the countryside. Retail magnate Edgar Kaufmann Sr., his wife, Liliane, and son Edgar Jr. were among those with mountain retreats.

On 2,000 acres they owned in western Pennsylvania’s rural Laurel Highlands they fished, swam and hiked. In 1935, Edgar Sr. decided to build a “modest cabin” to replace their formerly crude accommodations.

At the urging of Edgar Jr., who had studied under Wright, Kaufmann tapped the famous architect to conceive a house. Wright’s task was to highlight a dramatic 30-foot waterfall in Bear Run Creek.

Instead of maximizing views of the creek, as Kaufmann presumed, Wright brought the water to the living space. The cantilevered terraces are an obvious expression. The tour reveals a windowed hatch on the main floor, where Mrs. Kaufmann would descend 17 steps into the creek and practice her fly fishing.

Visitors also should be attentive to the art. A guide was so busy doling out details — such as that all stone was quarried within 500 feet of the house — that we could have missed a Diego Rivera, Untitled (Portrait of a Man), ca. 1930-40, in the guest bedroom. Hundreds of art pieces throughout the house included two pieces by Picasso.

Knowing the basics frees one to observe even more details. For example, all bathrooms are lined with cork panels because the material is natural, soft, waterproof and sound-absorbent.

But that is jumping ahead. Summers are busy at the Fallingwater, so timed reserved tickets are mandatory. And that may require a two-week advance purchase. Late fall months are less busy and Fallingwater is closed in winter.

Guests drive into a wooded parking area and walk through the woods to the Visitor Center, where they are required to leave most bags. A gravel path — not a walk for the disabled— drops to the main house. At a bridge, visitors are told interior photos are forbidden. The guide will let them know when and if cameras are permitted (on the main terrace) and a wooded overlook spot.

The first floor has an open-floor plan, something uncommon at that time, with spaces extending for entertaining. Much of the black walnut furniture is built into the structure, as Wright sought unity with all things in a home.

By now, visitors can see the controlled palette, chosen by the architect. He specified his favorite Cherokee red to cover the steel window sash and ochre for the cement work — colors he favored for projects throughout his career.

The second-floor guest room has a private bath on the east end. That’s where the Diego Rivera hangs on the east wall just above the headboard. A little farther west is a master suite with separate bathrooms — and even bedrooms — for the active couple. Wright believed each person deserved their own “space,” and the Kaufmanns were indulged.

Entering each room, visitors will notice a step down in the ceiling. Wright did that intentionally to redirect the eye to the wall of windows. And windows are essential in Fallingwater. They transfer attention to the trees and water outside.

The third floor was Edgar Jr.’s domain. It includes a sitting room and bedroom.

If the Kaufmanns sold and celebrated grandeur and artifice in their Pittsburgh retail palace, Edgar Jr.’s room shows how they kept Fallingwater structured, linear and minimalistic. His bed, for example, was simple and simply adorned.

A covered path leading uphill connects Edgar Jr.’s suite with the 1,700-square-foot guest house that mimics the colors, terraces and design of the main house.

Fallingwater evolved far beyond the “simple cabin” of its conception. And it went far beyond Wright’s original cost estimate of $35,000 (about $620,000 in 2016). In fact, the cost for the house in the 1930s was $155,000, which included $8,000 in architect’s fees and $4,500 for built-in walnut furnishings. That’s about $2.7 million in 2016 dollars.