"Piet (Mondrian) in Pittsburgh," at The Andy Warhol Museum, pairs three of the bold geometric images most frequently associated with the Dutch artist (1872-1944) with 15 earlier paintings that, together, give a fascinating look into the experimentation that led to his most acclaimed work.

The paintings, completed between 1907-27, reflect both the changes that were occurring in art at that time as well as the turmoil in Europe.

A small abstracted landscape, "The Red Cloud," an oil on cardboard circa 1907, is sensual in brushstroke and color. It's one of several early works loaned by the Gemeentemuseum Den Haag of The Hague. "The Mill," of 1908 and from Amsterdam's Stedelijk Museum, comprises a windmill towering over a tortured landscape of brick reds, salmon and blues.

Mondrian lived in Paris from 1911 until World War I, and again between wars, and the influence of cubism appears as surfaces begin to break apart. In the series "Compositions in Oval," color takes a subordinate role as dark lines fracture and activate the canvas.

Ultimately his expression is reduced to clean planes, the brushstroke restrained, color limited to black, gray and white and the primaries -- yellow, blue and red. It is Mondrian at his most elegant, and the paintings continue to enthrall.

"Mondrian" continues through Aug. 31. Hours are 10 a.m. to 5 p.m. Tuesday through Sunday and until 10 p.m. Friday. Admission is $15, seniors $9, students/children $8, 5-10 p.m. Friday half-price. For information, call 412-237-8300 or visit www.warhol.org.

Franklin Park Conservatory in Columbus, Ohio, has become the first botanical gardens to be lit by James Turrell, the internationally exhibited light artist whose works are in the collection of the Mattress Factory and whose extensive exhibition marked the silver anniversary of that North Side museum in 2002.

"Light Raiment," a permanent installation that employs more than 7,000 LED bulbs to "fill [the Franklin's 1895 Victorian Palm House] with volumes of changing light and color," was supported by a $1 million gift. The program runs from dusk to dawn and is visible from the street. Rooftop cocktail hours are 5:30 to 10 p.m. Thursdays through October (except Sept. 18) for closer viewing.

Another Pittsburgh link is that Franklin Park hosted a Dale Chihuly exhibition in 2003-04, as did Phipps last year. Columbus purchased most of the work from its show, and Turrell and Chihuly discussed the effect lighting would have on the few glass pieces currently displayed, according to conservatory spokeswoman Carly Gerdeman.

The entire Chihuly collection will be reinstalled in fall 2009. Opening Oct. 4 is "Bending Nature," an exhibition of works by 15 nature-inspired artists, including new works by Dorothy Gill Barnes and Dennis Oppenheim, and documentation of works by Andy Goldsworthy and Robert Smithson.

Information: 1-800-214-7275 or www.fpconservatory.org. To view a good multimedia piece on the light installation by The Columbus Dispatch, click on "Light Raiment" and then on "click here."

Another significant contemporary artist with Pittsburgh relevance is Louise Bourgeois, whose retrospective exhibition is at the Guggenheim, New York, having toured London and Paris. Bourgeois' 25-foot-high bronze fountain and granite benches resembling eyes are installed in Katz Plaza, Downtown.

The show offers a walk through the artist's psyche as well as through artworks that span early paintings to recent sculpture, each object inextricably entwined with emotional agitation that lingers from childhood disappointments.

"The subject of pain is the business I am in," Bourgeois is quoted as having said in the 1991 Carnegie International catalog. The sculpture "Cell II," in the Carnegie Museum of Art collection and one of six "Cells" exhibited in 1991, has been loaned to the retrospective.

A short video and archival photographs in the somewhat elusive Sackler Center are worth seeking out for images of Bourgeois' early life and candid comments by the quintessentially feisty nonagenarian. The audio tour, included with admission, is informative.

"Louise Bourgeois" continues through Sept. 28 (1-212-423-3500 or www.guggenheim.org). A documentary about the artist, "Louise Bourgeois: The Spider, the Mistress and the Tangerine," received limited theatrical release in June.