A graph of symbols in Kabbalah (A mystery sect of Judaism which built around the mystery interpretations of "Torah"). It represented, as a diagram, the physical rendition of the 3-dimensional images of the spiritual realm. The same diagram can also be found in Gendoh's office.
The diagram is composed of ten circles linked by 22 paths. It shows the route of how a human can attain the highest possible spiritual level. Moreover, many other interpretations are said to be possible: As a step-by-step diagram for meditation, as a map that shows the way to wisdom, or as a prediction for human's future etc.
In ep.26 'Magokoro wo kimi ni", EVA series formed a big Tree of Sephiroth on the sky.