The pattern
Trees, pillars, mountains, ladders and rivers connecting upper, middle and lower worlds appear across Siberia, Inner Asia, northern Europe and parts of the Americas.
Eliade's synthesis and its problems
Eliade's 1951 Le Chamanisme organised these motifs into a single archaic technique of ecstasy. His reading has been criticised for cherry-picking sources, privileging 'pure' archaic forms, dismissing possession as degeneration, and building a system his sources do not support.
Reading the motif honestly
Widespread is not universal. Similar structures can arise from similar environments, from diffusion, or from the analyst's own template.