Four iterations of a "box fractal" or "Vicsek fractal", derived by iteratively replacing a square with a saltire or cross of five smaller squares on a 3-by-3 subgrid.
Top:  Four iterations of the saltire form of the fractal.

Bottom: Four iterations of the cross form of the fractal.  The second iteration is a form of the "cross crosslet" symbol of traditional heraldry.
Self-made graphic, converted from the following vector PostScript source code:

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%EOF
AnonMoos