100 million handmade porcelain sunflower seeds filling the Tate Modern, by one of the most important artists of our time, Ai Wei Wei. (technically the individual seeds were made by these really nice highly skilled porcelain workers without enough work
Spectrum of Time, Rainbow Sundial calendar by Peter Erskine. "Visitors walk inside a living map of the solar year. Each "Rainbow Sundial calendar" is a unique joining of astronomy, architecture, locale, and art.