Kamui's Dimension

The Other Dimension is an alternate space that can only be accessed through the use of certain Space–Time Ninjutsu. While it is unknown if all Space–Time Ninjutsu are somehow connected, Kakashi Hatake's Kamui and Tobi's Space–Time Migration apparently share this same dimension when teleporting objects, evidenced by the fact that objects warped by the former ability were still able to interact with Tobi despite his otherwise comprehensive intangibility. Kakashi exploited this apparent connection to injure Tobi in the battle between them, during the Fourth Shinobi World War.

Appearance
The location was first observed once Tobi transported both Sasuke Uchiha and Karin there after their battle at the Five Kage Summit, where it was shown to be composed from an innumerable amount of randomly arranged and differently sized rectangular prisms.