ON is home to a phenomenon not quite unique, as it is found on other worlds created by, well, the creators, but no less peculiar. For all the investigation that has been done, this phenomenon is first and foremost called Impossible Space (IS). There are three volumes on ON in which IS occurs, the extreme density zone at 93.000, 93.000, 93.000 (designated IS-EDZ), through one of the doors in The Block (designated IS-Block), and behind an otherwise freestanding door in a field at -93.000, -93.000, -93.000 (designated IS-Free). All of these spaces display unique characteristics, as do all builder related ISs.