Onam 2013 in Bangalore. The pyramid structure with four faces and a flat top is an abstract icon of the Vamana-Mahabali Hindu mythology. The tallest one represents Vishnu's avatar Vamana after metamorphosis into a giant form for the three steps. It is used for Onam celebrations, called Thrikkakara Appan or Thrikakkarappan (Sanskrit: Trivikrama). Onathappan.