Traveling to Spain in 1936, Escher visited the Alhambra for the second time and visited the mosque in Córdoba. The renewed exposure to Arabic design occasioned an important change in his work — he became fascinated with geometry and symmetry and how those abstract design elements could be incorporated into his representations of the natural world. The images in his later prints are created from within his mind rather than representations of the physical world. He explored how to represent people, animals, and objects rising from the flat page and then returning, as well as how to represent the endlessness of infinity.
Browsing through these takes me back to my college days. I don’t know what the situation is now, but when I was in school, it was almost a requirement that 50% of the dorm rooms on any given floor had to have an M.C. Escher poster hanging on the wall. (via @john_overholt/status/992397947471089669)