Underground airplane factory Rabstein
In the valley of the Kamnitz there were two underground aircraft factories. Originally 80 000 square meters were planned, but only 4500 meters were completed.[1] Not only parts for Messerschmidt-aircrafts, but also complete helicopters of type FA 223 were built here under perfect camouflage.[2] Later, the Contracting States of the Warsaw Pact used it as a tank depot, which had a capacity of 8 million liters.[3]
[1]: According to: https://oiger.de/2017/04/20/die-flugzeugfabrik-im-bunker-teil-ii/163300#45_Kilometer_Stollen_vorangetrieben
[2]: According to: http://www.team-bunkersachsen.de/pages/u---verlagerungen/zechstein-werk-b.php
[3]: According to: https://www.battlefieldsww2.com/rapstein-zechstein.html