For half of my life, I've spent a lot of time enjoying the museums, gardens and public buildings along the National Mall. Once in a while the view takes me by surprise, thanks to an angle I never noticed or an unexpected change in the weather. On a late winter day, looking out from the National Gallery's West Wing I watched the sun pierce the roiling clouds. There, beyond the trees, was the silhouette of the Smithsonian Castle. Sunshine came and went. Art was all around me. The sun and clouds continued their dance.