Modern humanoid sculptures previously reported include the commanding Angel of the North and the divisive iron figures at Crosby Beach near Liverpool.  But they don’t come any more mysterious than the Time Guards (or Timeguards) by Austrian artist Manfred Kielnhofer, which have a habit of appearing abruptly in public places one day and vanishing the next.

Source: Guardians of Time: Mystic Sculpture by Manfred Kielnhofer | Urban Ghosts