This is a beautiful piece of symmetry art by Dr. David Annal, the first webmaster of Tessellations.org.
Can you decide whether this is a tessellation?
Scroll down to the bottom of the page to see webmaster Seth's opinion.

Is This a Tessellation?
Webmaster Seth's Opinion: "No".
The basic shape repeats perfectly. If this were just empty shapes, it would be an OK and slightly boring tessellation.
However, if this is a picture of houses, the answer is emphatically "no" because we can't see the whole front of each house.
Those red roofs covers up the lower part of the houses behind them.
Although the outlines fit together like a proper tessellation, we shouldn't ignore that the motif is houses--
houses with their lowest part hidden behind other houses.
A proper tessellation should fit together without gaps or overlaps.

This abstract shape tessellates. It's a proper tessellation.

This is not a proper house. The first floor is half gone! It does NOT tessellate, because it looks like the houses overlap.

This is a proper house, but its shape doesn't tessellate.