The Glenstone Museum sits on 230 acres in Potomac, Md. (Goran Kosanovic for The Washington Post)

When you visit the expanded Glenstone Museum, you may find the contemporary artwork to be moving, provocative, weird or simply inscrutable, but one aspect of the experience will be constant: its mindfulness.

The desire for an unmediated meeting of artwork and viewer is the defining objective at the museum campus in Potomac, Md., and is achieved through its own state of applied thoughtfulness.

You will find it in the way that the new galleries are expansive, naturally lit and cellphone-free, that the number of visitors is limited to about 400 daily and the transactional areas — for tickets, shopping and eating — are physically removed from the gallery spaces.

But the most potent if understated factor in this bid for active tranquility is in Glenstone’s landscape design, which marries its old topography to the new, while more than doubling the amount of outdoor space to 230 acres.

Its scale and pastoral character call to mind the enduring compositions of rolling pastures, lakes and woodlands by 18th-century English landscape designers. At the heart of Glenstone’s idyll is not a stately home but the Pavilions, a cluster of towering concrete cubes.

Glenstone is the creation of a low-key couple, wealthy industrialist Mitchell Rales and Emily Wei Rales, an art curator who began her career in New York galleries. Glenstone’s first phase opened in 2006 and centered on a museum named the Gallery to showcase some of their foundation’s extensive collection of major modern artworks. These extend to outdoor sculptures by Jeff Koons, Andy Goldsworthy, Tony Smith and Richard Serra. The Gallery remains, but the center of gravity has shifted 900 feet northwest to the Pavilions, shrouded during several years’ construction. Phase II opens Thursday as a nearly sixfold increase in museum space around a large formal water garden.

Acres of wildflower meadows surround the Pavilions, the Koons floral sculpture called “Split-Rocker,” and on the original east side of Glenstone, down to the main wooded stream and the Raleses’ contemporary lakeside home. Both the house and the Gallery were designed by architect Charles Gwathmey, who died in 2009. The Pavilions and other new buildings — totaling 240,000 square feet — are the work of architects Thomas Phifer and Partners, of New York. The landscape architecture has been in the hands all along of PWP Landscape Architecture, based in Berkeley, Calif., and headed by the noted modernist landscape architect Peter Walker, who is now 86.

Designed by architect Thomas Phifer and Partners, the Pavilions represent a nearly sixfold increase in gallery space at the privately owned museum. (Goran Kosanovic for The Washington Post)

At Glenstone, the original wooded areas, almost 80 years old, form a matrix for new trees that in a few years will provide an integrated forest of native hardwoods threaded across the whole site.

Approximately 8,000 large trees were planted to create the future forests. Two hundred existing trees were moved, each carefully, laboriously, and in the case of the largest specimen — a fully mature sycamore — using the same techniques as you use to pick up a historic frame house and relocate it.

The task of the landscape architect is to present a place that seems to have been forever there, and this was a big task at Glenstone, not just for its sheer scale but because PWP’s Adam Greenspan and his team were trying to bring cohesion to a location that was a typical hodgepodge of land parcels in outer suburbia. The palimpsest includes a fox hunting club, an alpaca farm, a grandiose neoclassical lakeside house, and a community of nine houses.

“Getting everything as connected and sinuous as possible was something we worked hard to do,” said Greenspan.

The nine houses were acquired individually, successively by Glenstone and eventually the street, houses, driveways, outbuildings and swimming pools — all the trappings of suburban Potomac — were erased so that the slow, leafy arrival to the museum by automobile sets you up for the ensuing passage by foot. (The cost of Phase II is about $200 million.)

Visitors park in one of three closely grouped lots, each organic in feel and materials. The paving is a light, crunchy gravel, the row dividers are of rough hewn stones, and the lots are defined by bosques or groves of tree species — the main lot of a sycamore hybrid named Columbia, the two smaller ones of red or white oaks.

You make your way along a curving, wooded pathway to the tree-veiled Arrival Hall, and then proceed on what seems like a casual 10-minute walk to the Pavilions, but which is highly orchestrated. The museum suggests an Italian hill town and the walk becomes the pilgrimage to it.

Take time to stop at key points to savor moments where slow perambulation leads to greater revelation. Once you’re across the bridge over a stream, a pair of sycamores (the one on the left is the one that was moved) frame your first glimpse of the Pavilions. The discrete towers suggest a cluster of buildings but are actually one structure joined below ground.

As you move through the snaking path into the open meadows the towers are more fully revealed. Look to your left and you see the distant, cockeyed head of Koons’s “Split-Rocker,” a “topiary” of flowers in the shape of two rocking toy heads halved and grafted together. Its bizarre size — rising 37 feet and containing 24,000 flowering annuals — is overpowering up close, but here, several hundred feet distant, its whimsy seems more accessible. As you approach the museum, the vista is closed down again as a woodland projects from the left. Last, the walkway becomes arrow straight, picking up the formal geometry of the Pavilions.

The idea of using paths and earthworks to direct the course through a garden, to frame its views and evoke an emotional response, is not unique to Glenstone. What is remarkable is the degree to which the tempo of the landscape experience has been composed.

“Time gets elongated in a way most people don’t experience these days,” said Greenspan.

Repeat visitors will come to find favorite spots in the landscape, and chances are those areas will be defined by trees. One of the most cosseting points is the wooded area established by the relocation of three sycamore hybrids that now form the canopy of a shade garden where the Pavilions, the Cafe, and the administration building come together. With under-plantings of dogwoods and ferns, it is already a potently calming place.

The sycamore trees were planted as large nursery stock in 2005 next to Serra’s wavy steel “Contour 290” but were beginning to crowd the sculpture. Last year, they were dug and transported 900 feet to their new spot. The rootballs were about 19 feet in diameter, and the trees were moved on cylindrical air bladders, fed from back to front as they proceeded, as you imagine stone blocks were rolled on logs to the pyramids.

Is there anything I don’t like? Some of the steep grading of the meadow around the Pavilions seems forced, and some of the new trees appear needlessly large and too closely planted. Greenspan said at key locations, the trees needed to establish their presence from the outset. And smaller trees would have been harmed by deer browsing.

Two other tree groupings are of note: On one side of the Pavilions, a meditation room named the Viewing Gallery invites study of the landscape beyond the glass wall. The vista, seasonally shifting, is of an undulating meadow that rises to a ridge topped with a thicket of honey locust trees.

To the east of the Pavilions, a viewing balcony invites study below of “Compression Line” by Michael Heizer. The sunken metal sculpture is formed by the pressure of the surrounding soil. (Goran Kosanovic for The Washington Post)

On the other side of the museum, the view out is to a slope with an unusual planting of copper beeches, purple-leafed trees that will look particularly colorful and fresh in their spring growth.

Historically, designers of pastoral landscapes were driven by aesthetics, albeit in the service of some worldview. Greenspan notes that at Glenstone, a key additional imperative is to embrace ecological goals. Some are obvious in the naturalistic woodlands and meadows of native flora, and in less obvious ways: The restoration of the once eroded and compromised streams, the land shaping to direct and absorb storm water and an organic approach to the horticulture. The meadows, for example, will take several years to reach their desired balance of grasses and wildflowers as weeds are beaten back through a careful mowing regime rather than using herbicides. (An environmental center will demonstrate sustainable practices).

One of the most dramatic displays of native flora, paradoxically, takes place in the most structured garden, the formal interior Water Court of the Pavilions. In its scale alone — 260,000 gallons covering 18,000 square feet — it is uncommonly large, and its mix of aquatic perennials, which includes almost 5,000 rushes, waterlilies, irises and cattails, promises dynamic shifts throughout the year.

A platform and bench are set at one end, but there is no boardwalk through the ponds. This is a viewing garden and a reflecting pool that reinforce the calming principle, not an immersive garden for plant geeks or dragonfly-photographers.

The design team had considered a Zenlike grove of trees for this space, Greenspan said, but the trees would have grown in bulk and height and started to compete for attention with the architecture. The water court also reinforces the intent of the landscape as a dynamic and evolving ecosystem, he said.

In its broadest sense, Glenstone seems to offer a new path for an outer suburb whose residential ostentation seems played out, even as new “chateaus” are being built. “This is one response to suburbia cycling down,” said Greenspan. “Showing how these kinds of places, expanses of land, can be valuable in a variety of ways. Culturally, but also ecologically.”

In its ability to lead us toward beauty and contemplation and away from the clutter, noise and distraction of a febrile age, the landscape at Glenstone promises to prove at least as important as the artwork.

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Glenstone’s expansion will open to the public Thursday. Admission is free, but reservations are strongly encouraged. For more information visit Museum hours are 10 a.m. to 5 p.m. Thursday through Sunday.