A pointer to a neat picture book featuring very many "space filling" curves: Jeffrey J. Ventrella: Brain-Filling Curves: A Fractal Bestiary, LuLu.com, (2012). The book can be downloaded for free at http://archive.org/download/BrainfillingCurves-AFractalBestiary/BrainFilling... Warning: it is a hefty 235 Megabytes! Two pertinent URLs are http://www.fractalcurves.com/HorrorVacui.html (book as html) http://www.brainfillingcurves.com/ (needs scripting activated) On page 107 (top) there is a curve corresponding to the L-system (and turns of 120 degrees) Start: F Rules: F --> F-F+F+FF-FF + --> + - --> - Here is a rendering http://jjj.de/3frac/R7-x1-curve.pdf What Ventrella does not show is how neatly 3 of these combine into either http://jjj.de/3frac/R7-x1-closed-trihook.pdf or http://jjj.de/3frac/R7-x1-closed-gosper-island.pdf The better known splittings of Gosper's island are http://jjj.de/3frac/gosper-split7.pdf and possibly (3 renderings) http://jjj.de/3frac/R7-2-gosper.pdf http://jjj.de/3frac/R7-2-sty1-gosper.pdf http://jjj.de/3frac/R7-alt-hex-gosper.pdf Here is a bubbly one: http://jjj.de/3frac/R7-bubble-gosper.pdf (cf. http://www.fractalcurves.com/Root7.html ) For the truly bored there are more images under http://jjj.de/3frac/ Best, jj