It's the perfect postcard image, a structure both sober and humorous. Cupolas climb atop each other with whimsy and enthusiasm. The building opens its arms to everyone who sprawls in the grass.

This is a building devoted to joy.

Robert Rietow's genius could be subtle, revealed as much by what a building didn't do as what it did.

"They had a program at the band shell commemorating the building," said Rietow's widow, Dottie. "And my son was part of that. The bandleader came over to say you should tell your dad that he moved the stage from the original position just enough so the sun wasn't directly in his eyes when the musicians played there."

Meticulous details make for a good building. One day, Rietow started a notebook of all the buildings he had ever worked on.

"He started that the day after he found out he had Alzheimer's," Dottie said. "He went back to the office and set the date he would retire, because he did not want to make any mistakes. Then he started to put together a notebook. His life's work."

The Rietows took trips to Egypt and Europe, where he took more than 5,000 pictures, amazed by structures from the humble to the grand.

"He marveled at what people could do with what they had," Dottie said. "When you think of how they were built, it was incredible. He had an architect's eye, but also an eye for beauty. For what man could do."

The band shell is happiest full of song, surrounded by summer crowds. Passing it in winter, it can seem impatient for spring, for the sound of the pennants snapping in the wind, the gust of music blaring out over the lake to usher in the sunset. But empty on a winter day is the best time to appreciate it for the gift it is, and to see the hand of its creator.