Kielnhofer's most famous work is, "Guardians of Time. Drawing on religious and supernatural phenomena, the Guardians of Time are stone statues that are cloaked in hooded robes and situated to seem like they are moving forth in some kind of ritual. In some cases the figures stand alone; in other instances, they are grouped together as if whispering to each other. Kielnhofer places his statues in public places like ancient castles, old mines, plazas, and parks. They are installed and moved without fanfare, heightening the eerie, mystic aura they give off. The first of these mysterious figures was created in 2006. Since then, Kielnhofer continues to create and install these statues all over the world.