The Black Gate is a Roman tower near present-day Trier that once served as a gate through the old city walls. It is considered by many to be one of the best surviving examples of Roman fortifications.
In 2072, it is the location of a secret ApostleCorp lab and the teleport to Antarctica. The Knights Templar have staged an attack on the facility, killing all ApostleCorp personnel except for a single Gray, and plan to use the teleporter to travel to JC Denton's Sanctuary and kill him. Both Tracer Tong and the Illuminati send Alex D to clear out the Templar forces, and the WTO occupies it afterwards. The base itself is mostly guarded by Templar Paladins and turrets, but a single RB-76 Military bot has managed to hold the square against all SSC forces.