It is the place where Numberblocks learn to master the way of the rectangle or it's just Twelve's meditation area.
Appearance
The retreat is a brown color (but a bit tan) near the beach with shapes of 12 everywhere. The floor is 12's blocks and there is a little balcony off to the side. The area 12 is in as seen in this image, has 2 openings, one on the left side and one on the right side.
There is also a gong a little far away from the right opening that 6 and 8 slammed into.