Parisians relax on an island in the River Seine on a Sunday afternoon: couples strolling, a woman fishing, a soldier, children, dogs — and a monkey on a lead.

But nobody seems to move. Seurat painted the scene not with ordinary brushstrokes, but with countless small dots and dabs of unmixed colour placed side by side, a technique later called pointillism. Up close, it dissolves into confetti; step back, and your eyes mix the colours into shimmering light.

He spent about two years on it, making dozens of studies. At around two by three metres, it's huge. The result is oddly hypnotic — part sunny afternoon, part frozen dream.