Nowhere is a completely empty, infinite white void of absolute nothingness (except for some colored square panels that do nothing but disappear when one tries to move them). It is visited by Squidward in "SB-129." After being chased out of the past by Primitive Sponge and Primitive Star, the time machine he travels goes haywire, after he broke the switch, and transports him to this white wasteland of loneliness.
At a first glance, there appears to be nothing at first, but walking down a bit further reveals some different colored square panels on the "floor" and "ceiling" of the dimension. There are also some strange voices that can be heard and every sound made is echoed, that also includes The Alone Group echoing "alone" in a rather disturbing way.
Nowhere seems to be absolutely nothing, nothing physical, no trace of life, just plain emptiness that seems to go on forever so it can be assumed that absolutely nothing or nobody is here because it is the end of time.
It is very likely that the dimension is the same as the Doodle Dimension, both sharing similar factors. If this is the case, we know that Nowhere is a dimension that can support the same capabilities as the Magic Pencil.
When Squidward first enters here, he seems to be the only thing visible in this lonely place. As he walks along further, he finds square tiles that he can lift up (which then float up and then disappear after doing so). After summing up that SpongeBob and Patrick are nowhere within sight, he relishes the fact that he found a place where he can be all to himself and with nobody else around.
However, after he hears many voices echo "Alone", he becomes frightened. He then attempts to get out of the terrifying nothingness by running, hoping to find its edge or some sort of exist. However, Squidward keeps looping right back to where he started from, implying that there is nowhere to go in this realm but into infinite nothingness in all directions. (Squidward, however, doesn't seem to be aware of the fact that he is looping). After looping back four times, Squidward notices the time machine, and really nothing else, is anywhere to be found.
After stomping the floor, four times, he finds the time machine again after falling through its ceiling. Squidward then finally breaks down, begs to go home, and admits he misses SpongeBob. After he speaks the final sentence, Squidward is finally able to escape the realm.
In the background, there is a pink panel and a yellow panel, both on the ceiling. They may be meant to resemble SpongeBob and Patrick.
There is an error during the scene where Squidward first arrives at "Nowhere." When he discovers the colored panels, he tries to lift up the cyan-colored one before it floats up and disappears. However, when the scene zooms in (actually out on Squidward himself), this same panel re-appears for a few moments in the same place it was before.
The panel is also a slightly different color shade than the first time.
Nowhere seems breathable for creatures who normally need water in order to breathe, an obvious example is Squidward. In Nowhere, there doesn't seem to be any water at all.
It's unknown how the physics here work, as when Squidward runs far away, he ends up in the same place and is apparently above the time machine the whole time.