A massive ruined tower located on the central island of the Aquvy archipelago. Stretching miles and miles into the sky high above the clouds it has existed since the dawn of human history. No one has been inside the tower or has even been able to get close to it for over 500 years because the Ethos Society has sealed its entrance with a powerful barrier. The Ethos say it's a cursed place. In truth it is actually a part of the Eldridge, a massive colony vessel which crash landed on the planet 10,000 years ago. The aerial nation of Shevat was once anchored at the top of the tower, which was the only way to access it from the ground without the aid of a flight-capable vehicle. After the Shevat-Solaris War 500 years ago the flying nation detached from the top of the tower and became nomadic. It has wandered the skies ever since and occasionally returned to Babel Tower at certain points but never reintegrated with it. For some reason, a massive adjustable mirror existed on the tower and was used in conjunction with Ft. Jasper to destroy the Solaris Gate buried beneath the Ethos HQ. The destruction of the third and final gate caused Solaris to phase back into synch with the rest of the world again for the first time in 500 years. It is fairly obvious when seen from the inside that Babel Tower is not of the Xenogears world. In spite of its decrepit state, it is filled with equipment and technology thousands of years beyond anything the people living on the Xenogears planet could have created.
Babel Tower was based on the real life Tower of Babel, an attempt by mankind to build a ziggurat high enough to withstand another global flood and thus defy God (all this despite his promise to never flood the entire Earth again). The account of Genesis states that the structure's construction failed when God intervened by confounding the language of mankind. Man was divided into language families, preventing communication for a time, so the building's construction was ultimately halted. A complete understanding of the event may be read at http://creation.com/linguistics-questions-and-answers.