It has been suggested by Romanian religious historian Mircea Eliade that architecture of sacred places often reflects this role:"Every temple or palace — and by extension, every sacred city or royal residence — is a Sacred Mountain, thus becoming a Centre." Pagoda structures in Asian temples take the form of a stairway linking earth and heaven. A steeple in a church or a minaret in a mosque also serve as connections of earth and heaven. Structures such as the maypole, derived from the Saxons' Irminsul, and the totem pole among indigenous peoples of the Americas also represent world axes. The calumet, or sacred pipe, represents a column of smoke (the soul) rising from a world center. A mandala creates a world center within the boundaries of its two-dimensional space analogous to that created in three-dimensional space by a shrine. In the classical elements and the Vedic Pancha Bhoota, the axis mundi corresponds to Aether, the quintessence. Plants Plants often serve as images of the axis mundi. The image of the Cosmic Tree provides an axis symbol that unites three planes: sky (branches), earth (trunk), and underworld (roots). In some Pacific Island cultures, the banyan tree — of which the Bodhi tree is of the Sacred Fig variety — is the abode of ancestor spirits. In Hindu religion, the banyan tree is considered sacred and is called ashwath vriksha ("Of all trees I am the banyan tree" – Bhagavad Gita). It represents eternal life because of its seemingly ever-expanding branches. The Bodhi tree is also the name given to the tree under which Gautama Siddhartha, the historical Buddha, sat on the night he attained enlightenment. The Mesoamerican world tree connects the planes of the underworld and the sky with that of the terrestrial realm. The Yggdrasil, or World Ash, functions in much the same way in Norse mythology; it is the site where Odin found enlightenment. Other examples include Jievaras in Lithuanian mythology and Thor's Oak in the myths of the pre-Christian Germanic peoples. The Tree of Life and the Tree of Knowledge of Good and Evil in Genesis present two aspects of the same image. Each is said to stand at the center of the paradise garden from which four rivers flow to nourish the whole world. Each tree confers a boon. Bamboo, the plant from which Asian calligraphy pens are made, represents knowledge and is regularly found on Asian