S-curve
A gently reversing curve within a scene that carries the eye through the frame in a sinuous path.
In depth
The S-curve is the leading line's more elegant relative: it moves the eye more slowly, covers more of the frame, and creates depth through its own foreshortening. It appears constantly in landscape — rivers, paths, coastlines — and in the human body, which is why classical figure posing relies on it.
Examples in practice
A river winding through a valley draws the eye from the foreground to the distant hills in two unhurried sweeps.