Cats avoid shiny, transparent objects. Or at least in my country, there are significant number of people who believe so. Hence the popular ritual of putting used PET bottles filled with water wherever they do not want to see cats getting around.
Selection and placement of PET bottles intrinsically unveil the owner’s personality. Some use whatever bottles they consumed as beverages and place them in rather casual, even random manner. Others, like the owner of this apartment house, pursue aesthetic perfection.
Whether it is more effective in preventing cats would be a different story. Cats might even appreciate the beauty of man-made structure, thus spending more, not less, time strolling around.
by Takashi Sasaki (photograph by himself)