Koch Snowflake
The boundary of the Koch snowflake is the quintessential fractal. The iterations may be viewed by moving the slider back and forth. At each stage, each line segment is trisected and an equilateral triangle erected upon the middle sub-segment. The length of the boundary curve, which is continuous at each stage, increases without bound, multiplied by a factor of 4/3 from one step to the next.
Please also view my teragon and Peano curve applets, which bring together two of the most basic fractals: the Koch snowflake and the plane-filling curve.