2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67813We introduce a new geometric tool for analyzing groups of finite automata. To each finite automaton we associate a square complex. The square complex is covered by a product of two trees iff the automaton is bi-reversible. Using this method we give examples of free groups and of Kazhdan groups which are generated by the different states of one finite (bi-reversible) automaton. We also reproduce the theorem of Macedonska, Nekrashevych, Sushchansky, on the connection between bi-reversible automata and the commensurator of a regular tree.21 pages, 4 figuresGroup Theory20M35 (Primary) 20F05,37B15,20E08 (Secondary)text