This image is dubbed "Sky and Water which is one of the most iconic Gestalt images ever created. It falls into several areas including similarity, proximity and continuity. The multiple and closely related images creates complex illusion at first glance.
How does the viewer perceive this image? As a black circle over the lines or as white lines on a black background with gaps in between? It is common for a viewer to see the black circle first because it is a more dominant color.