It is a known fact that throughout his life Pessoa was interested in and conversant with an array of esoteric currents and doctrines. Underpinning that interest was a marked tendency to a form of symbolic thinking encapsulated in the lines "... my thinking is condemned / To symbol and analogy" from a 1907 poem by the incipient heteronym Alexander Search, which recur in a fragment from 1932 of the dramatic poem Fausto. Pessoa's continued symbolic thinking, informed by copious readings mainly in Western Esotericism, allowed him to develop a creative hermeneutical approach to esoteric epistemologies. This essay will be concerned specifically with Pessoa's conception of the mystical significance of geometrical forms, arguing that they not only enriched the figurative expressiveness of his poetry but also played a crucial role in his formulation of a poetics of Sensationism. Pessoa's use of geometric imagery will be considered in the context of the fascination with sacred geometry and exploration of its aesthetic potential displayed by other modernists, like Yeats and Pound, and by avant-garde movements from the early XXth century which were also driven by analogous concerns, such as Futurism, Vorticism, Cubism, Expressionism and Suprematism.