The Fraser Spiral Illusion is an optical illusion created by British psychologist Sir David Fraser in 1908. It is a two-dimensional pattern of concentric circles that appear to be a three-dimensional spiral. When viewed from a certain angle, the circles appear to be connected and form a continuous spiral.
From Wikipedia
The Fraser spiral illusion is an optical illusion that was first described by the British psychologist Sir James Fraser (1863–1936) in 1908.