Tessellations, and Tiled.art
Tessellations are the coolest — a figure interlocks with itself perfectly to fill the page, with no overlaps or gaps. I created the website Tiled.art to explore their many delights.
Here are some nice examples (click to open a full view on the site):
In the Tiled.art gallery you can see over a hundred more, from artists around the globe. And each artwork can be animated to show its underlying structure — try this one.
On the site you can also learn about the symmetries behind the art.
And you can create your own tessellation, with the shapes staying interlocked automatically. Here are a few of mine, created on the site (click for a full view):
Tiled.art is a free site, with no ads. I hope you enjoy it!
And for a quick preview check out this video.