The Unfound Door is one of the magical doors that Roland and his ka-tet come across while seeking out The Tower. Out of all the doorways to other worlds they run across this one is the most powerful and most influential. What makes this door so important and powerful is where it can lead the user. It has an unlimited reach, taking the user to any where and when they desire. The trick is that it can only be opened with Black Thirteen, Maerlyn's most dangerous of the Wizard's Rainbow. Throughout the series this door is seen in a few different places.