A standard gauge railway tunnel, codenamed "Ida", was to be built on a curving path that would connect it with both the east- and west-bound main line railway, allowing trains to run straight through the complex without needing to reverse or be turned around. This would serve as the main unloading station, where missiles and supplies would be offloaded onto trolleys that would transport them into the connecting galleries "Mathilde" and "Hugo". "Hugo" connected in turn with "Sophie", a dead-end railway tunnel branching from the main line into "Ida". Each of the main tunnels had a number of unnamed side tunnels of the same dimensions as the main tunnels and up to long. The central feature of the complex was a huge octagonal rocket-preparation chamber directly under the dome. It was never completed but would have been in diameter and up to high. A number of intermediate floors, possibly as many as ten, would have been built up the sides of the chamber.