On a recent sunny afternoon, art collector and patron Steven Oliver, 64, stands at the bottom of concrete cylinder. This is Oliver's most recent sculpture commission for his eponymous 90-acre Geyserville ranch, where he lives with his wife, Nancy. Designed by the sculptor and installation artist Ann Hamilton, some of whose work belongs to the Guggenheim, the tower was poured from 1 million pounds of concrete transported to Oliver's ranch in no less than 600 truckloads. The equivalent of an eight-story-high building, the tower has only one very tall story, which is open to the sky. Oliver's voice echoes as he asks, "You're not scared of heights, are you?"

He then leads the way up one of the two staircases still without railings (the structure isn't fully complete, so the banisters haven't been installed yet). A couple flights up, he stops to take a seat on a windowsill. He's not out of breath, he's just demonstrating how Hamilton designed the structure to accommodate the human body. After a moment, we continue. As the altitude increases, the width of the stairs decreases, and one feels an urge to hug the wall. Upon finally reaching the top of the tower, Oliver says, "I'm lucky to have this, but even more fun was working with her to design it."

Oliver's thirty-something son, Josh, is currently the project manager for the tower project, which has been in the making for two and a half years. When completed this fall, it will be used as a private musical experimentation and performance space, due to be christened by the Kronos Quartet.

On Sept. 15, the Arts Council of Sonoma County honors Oliver as part of its eighth annual Achievement in the Arts Awards. Locally, Oliver is the chairman of the SFMOMA board and has been a California College of the Arts trustee for 25 years. (He also holds an honorary Doctor of Fine Arts degree from that institution.) Nationally, he's served as a chairman for the NEA and as a trustee for the Smithsonian's Hirshhorn Museum and Sculpture Garden.

Known as one of the region's most noted and enthusiastic collectors of contemporary art, Oliver used to hate it. Accompanying his wife to museums while she was finishing up her degree in American studies years ago, he had two ideas about contemporary art. "First, I thought it was a pile of junk," he says with a laugh. "Then I thought, 'I could do that.' One piece [by Ed Keinholz] annoyed me so much that I went back during work the next day."

Did he like it better upon return? "No," he says, "I didn't like it any more, but I was less dismissive and more curious. That's the important part--it leads you to learn about yourself and the world."

The Olivers started collecting art in 1978, foregoing a vacation to purchase their first piece, a drawing by Jim Dine. In the 1980s, a few years after acquiring the ranch in Geyserville where he and Nancy raised sheep for an organic lamb supplier patronized by such as Wolfgang Puck, the couple became frustrated with art's increasing commercialization. Oliver says that he was dismayed by how much work "was tied to the financial pages." This dissatisfaction came to a head during a dinner conversation when a friend congratulated him on the business acumen of his collecting. This wasn't true; Oliver had never sold any of the pieces in his collection. The couple decided to start commissioning large, site-specific art that would be immobile. As such, they could not be put on the market as commodities.

Since commissioning Judith Shea to create the first piece in 1985, some 20 artists, many of them highly illustrious, have flourished at the Oliver Ranch. "I find changing the physical environment addictive," Oliver says, looking over the summer-browned landscape which is home to 18 sculpture and audio-art commissions, including a transitory project by environmental artist Andy Goldsworthy that has long since assimilated back into nature.

Bruce Nauman, named one of Time magazine's 100 most influential people in 2004, created a quarter-mile-long staircase snaking up from the edge of the property all the way to the Oliver home. This sculpture is what prompted the couple to end their stint as shepherds, as the piece was to wind directly through the sheep's breeding and weaning areas. Nauman's untitled steps are the only sculpture visible from the road, and barely at that--the muted color of the concrete is camouflaged by the earth tones of the hill.

Oliver has an unusual background for an arts patron and advocate. He is an engineer and has been in the construction business since his 20s. As president of his own highly successful construction firm, Oliver & Company, he has built several North Bay beauties: Far Niente Winery, the Charles M. Schulz Museum and Research Center, and the Oxbow School.

His construction and engineering background makes him a very hands-on collector, facilitating the fabrication of the giant sculptures around the property. "You dream it, we'll build it," he says. Oliver takes care of the engineering and the permitting aspects of the works, and even supplies an on-site live/work studio designed by David Rabinowitch and Jim Jennings, which is a remarkable piece of architectural art in itself.

"We free [artists] from traditional confines with no limit on size, scale, bulk or mass, within reason," he explains of the ranch aesthetic. "But [the artists will] limit themselves more than I will." Oliver likes watching the way artists solve problems and feels that his construction employees are better for being involved in the process, too.

Playing such a close role in the creation of the art thrills him, because it gives him more than just a first-row seat to the performance; instead, he gets to interact with the artists, often forming lasting relationships with them. "My children and grandchildren have grown up eating dinner with great artists at the table," he says. "You have this incredible, rich life experience by knowing these people."

Richard Serra, who worked on a series of sculptures Snake Eyes and Boxcars between 1990 and 1993, recently invited Josh to his opening in Bilbao. Oliver had to ask Serra, "Can I go, too?" (Serra had thought Oliver would be too busy.) "You can't buy that as a collector," Oliver says, drawing the distinction between simply collecting art that's already been finished and commissioning pieces that haven't yet been started.

By commissioning artwork, he and Nancy are often the first people privy to seeing an artist enter a new period in his or her work. Thus, Oliver has a multitiered relationship with the artists he patronizes. They are part family, part collaborators and part idols. "Artists are the greatest minds in the world," he proclaims. From changing his political sway to making him reconsider seemingly insignificant habits, artists have shaped Oliver just as much as he's helped them give concrete form to their ideas.

Modestly, he says, "I'm a glorified studio assistant."

Brushing aside recognition for his own creative talents, Oliver begins the long walk back down the tower's steps. He explains, "I'm a facilitator. I'm creative in solving the problem, but I'm not creative as in making the problem."

Making the problem is what Steven Oliver lets artists do best.

Steven Oliver is honored at the Achievement in the Arts Awards on Friday, Sept. 15. A dance performance, conversation with 'San Francisco Chronicle' art critic Kenneth Baker, dinner and wine complete the evening. Hyatt Vineyard Creek Hotel, 170 Railroad St., Santa Rosa. $150. 707.579.ARTS.

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