Is Nadia's Bell part of the geographic region of the Dead Sea, or merely a connected area of space-time? Why does Miguel call it Time Crash Ground Zero?
Miguel's exact statement about the area being the epicenter of the Time Crash:
Welcome to the Tower of Geddon... Time Crash Ground Zero!
It seems that Miguel was speaking directly about the Tower itself, which certainly is the center of the Time Crash, as it resides precisely where Chronopolis would have been in the Sea of Eden. What, then, is Nadia's Bell doing there? Obviously Leene's Square from Chrono Trigger, how are it and a grand sunset accessable within a Tower of finite capacity? The answer lies in the fact that one must pass through a Gate to access it -- a spatial wormhole. The entire party under General Viper's command is frozen before this Gate, and it is also the last defense before one can reach Miguel and the Home World Flame. Thus, it is perfectly reasonable to label the Gate as such, and also classify it as a defense against access to the area Miguel was defending. Judging from the fate of the Acacia Dragoons and from Serge's success, only the Arbiter of the Frozen Flame and those in close proximity can pass. The Gate transports the party to Leene's Square and Nadia's Bell within that ruined timeline.
From: Common Questions