The Gosper island (Mandelbrot 1977), also known as a flowsnake (Gardner 1989, p. 41), is a fractal that is modification of the Koch snowflake. The term "Gosper island" was used by Mandelbrot (1977) because this curve bounds the space filled by the Peano-Gosper curve.
It has fractal dimension
(Sloane's A113211).
Gosper islands can tile the plane (Gardner 1989, p. 41).