Before architect Philip Johnson's death in 2005, sneaking onto the New Canaan property he shared with his partner, curator David Whitney, to see his modernist masterpiece, the Glass House, became a rite of passage for scores of Yale University architecture students.

"The trick was to see how long you could walk around before David Whitney kicked you off the property," said Yale-trained architect Chris Wolfe Nichols.

Now a Glass House lead tour guide, Nichols didn't take part in the trespassing ritual, but she knows many who did.

For decades, an invitation to spend time at Johnson's 47-acre home was one of the most elusive social gets in Fairfield County. Those lucky enough to be invited over for a chat, a martini and a tour of the grounds included neighbors Johnson and Whitney met at favorite New Canaan haunts -- bookstores and coffee shops -- and some of the most important artists and intellectuals of the middle to late 20th century.

In 2007, when the estate opened for public tours, tickets sold out quickly and the Glass House again gained a reputation for exclusivity. In the past three years, more than 15,000 visitors from 46 states and at least 30 countries have visited the site, according to Glass House Executive Director Christy MacLear.

"I meet people all the time who tell me, `You're sold out for years,' but you can get access to the site," MacLear said. "Many people in the design world had been waiting their whole lives to see it, and now many have."

Though tours remain popular, particularly with design professionals, artists and overseas visitors, tickets are available, especially for weekdays and later in the season, which lasts through November.

Heralded as the godfather of modernism and dean of American architects at the time of his death at age 98, Johnson was the first director of the Department of Architecture at the Museum of Modern Art. He designed or collaborated on landmark buildings such as the AT&T headquarters, the Seagram Building and its Four Seasons Restaurant, and the New York State Theater at Lincoln Center in New York; the Boston Public Library; and the Kline Science Center at Yale University.

Johnson left his New Canaan estate, along with an endowment for its upkeep, to the National Trust for Historic Preservation, a nonprofit organization that oversees site programming, including the public tours program. In recent years, the trust has purchased adjacent plots and extended the protected acreage around the house. With its 14 modernist structures, 200 whimsically landscaped acres in New Canaan and Stamford, and paintings and sculpture by the likes of Andy Warhol, Frank Stella and Jasper Johns, the Glass House property is "one of the best walks in Connecticut," said guide Perrie Ridley, of Ridgefield.

Structures there are as diverse as the central Glass House, a minimalist icon completed in 1949, and the postmodern Da Monsta, a building completed in 1995 that wouldn't look out of place on the set of a Dr. Seuss adaptation. Built without right angles, Da Monsta's red and black surfaces are visible to drivers passing by, as is the estate's 20-foot-high entrance gate made from a sailboat boom.

"This was Johnson's 50-year diary of his architectural genius and philosophy," said lead tour guide Susan Mahoney, of Greenwich.

Rectangular and circular structures dot the landscape. The rectangular Glass House, for example, contains a circular brick fireplace that breaks the plane of the opaque roof. The rectangular Brick House faces the Glass House like a shadow or negative image, but these two rectangular structures are offset and softened by a circular concrete sculpture by Donald Judd (Untitled, 1971) and a small circular pool on either side. Similar arrangements of angles and curves are repeated throughout the property.

"The entire estate is a kind of art installation," said lead tour guide and New Canaan resident Gwen North Reiss.

The site's 13 part-time tour guides, Johnson admirers all, keep the architect's playful spirit alive during their tours. During a recent tour, guide Mandy Maruyama pointed out the ribbons of alternating grass and gravel beneath visitors' feet as they made their way toward the Glass House, explaining that for Johnson, these outdoor elements served the same function a vestibule might in a traditional home. She also noted that Johnson liked the sound his guests' feet made as they crunched through the gravel to the house.

At another point during the tour, Maruyama, a Wilton resident, invited guests to picture Johnson wading through the silver meadow grass that separates the Brick House, where he slept, from the study, where he worked.

At the same time, keeping in mind one of Johnson's favorite pieces of advice -- "Shut up and look" -- tours are designed to incorporate long stretches of silence.

"He didn't want people to come and have a lecture. He just wanted them to come and enjoy," said Reiss, a poet and author who interviewed Johnson in 1999. "You can learn all you need to just by walking through the space. It was meant to affect your senses."

Some tours, like those Nichols sometimes leads for architects, can become highly specialized discussions. For example, she said, architects are often intrigued by the complicated, inefficient structure of the columns in the Glass House, a feature that has been questioned by several noted architectural critics over the years.

"People tend to think of him as minimalist, but he was coming up with structural moves that are very complicated," Nichols said.

Nichols, who worked for I.M. Pei on the Pyramide du Louvre project, said Johnson was important to American architecture because he was one of the first architects to use industrial materials such as steel and glass in residential design.

"He was coming up with a system of ornament using industrial stock-grade elements," she said.

Another lead tour guide, artist Tricia Wright, also leads specialized tour groups of artists and museum curators. Wright's groups often spend extra time in the Painting and Sculpture galleries, which housed the vast art collection Johnson and Whitney acquired over their 40 years together. Though much of the work has been sold to support the trust, works by artists such as Julian Schnabel, Robert Rauschenberg and Stella remain.

"I love the Frank Stellas," Wright said. "Every time I look at them, I get that sort of shock of pleasure."

Some of the 14 structures served precise functions -- the Glass House for entertaining, the study for work, and the art galleries for storage and display -- while others he called "follies," buildings too small or unusually proportioned to be lived in, such as the Lake Pavilion with its low ceilings or the Ghost House made of chain link.

"Many people may imagine that seeing the Glass House will be a dry,

museumlike experience. But it's so full of surprises," said Wright, who lives in Irvington, N.Y. "There is so much humor and beauty."

The landscape may be the biggest surprise. Gently manicured swathes of grass and gravel, the groupings of trees he liked to call outdoor "vestibules," the slopes and curves seem slightly too good to be true, too balanced and sublime to have occurred by accident. Of course, they didn't. Johnson meticulously plotted out where he wanted mounds of earth to be built up or shaved, where trees should be planted and removed, and where ponds and bridges would appear.

In Wright's words, "It's just as much about landscape as it is about architecture." Or as Johnson once explained to her, "It's all one art."

Wright noted that one of the most important artworks on the property isn't modern at all. The circa 1648 landscape, "Burial of Phocion," by French painter Nicolas Poussin, is placed centrally in the Glass House sitting area.

Sitting on the daybed designed by Mies van der Rohe, Johnson or his guests might have gazed from the painting's idealized landscape to a set of remarkably similar views. Out the back wall, onlookers are greeted by a grassy promontory that drops off suddenly to reveal a convex slice of Stamford's Rippowam Valley. The north and south exposures showcase sloping, tree-lined vistas that mimic the contours of the painting far too closely to be accidental. Johnson spent his last days looking at the painting and the idealized landscape he designed to mirror it.

"The Glass House is all about experiencing landscape from the inside," Nichols said.

Wright notes that the interplay between landscape and architecture means the site is always changing with the light, from hour to hour, season to season.

"If you live in an area with something like that, something that's so unique," she said, "it's something to be proud of."

Standard tours cost $30. Extended, twilight and private tours are $45 to $150. Tours begin and end at the Philip Johnson Glass House Visitor Center, 199 Elm St., New Canaan. Tickets can be ordered at www.philipjohnsonglasshouse.org or by calling 866-811-4111.