Globe thistle is a fun plant, one of those that stops passersby in their tracks. The flower heads form glowing constellations that seem to float above the leaves. It is native to Europe and central Asia and has on occasion escaped cultivation, but according to the Sunset Western Garden Book, is "Well-behaved." It thrives in full sun.
Just when you think the flowers are done doing what they do (growing larger, spikier, bluer), they do something else. Every spike turns into a tiny bloom, and the spiky globes turn into pom-poms.
In transition, with pom-pom in the upper left. The bee in the middle is impatient, unable to wait for the flowers to open.