- The Silent Castle is often associated in the incarnation as it is known in the comics. Originally, the name Silent Castle was never used nor was it ever referred to as such. The exact location was never revealed until issue #120 of the Marvel series. The visual style for the Silent Castle may have been taken from the animated mini-series, A Real American Hero, where it is often referred to as the Cobra Temple. The animated mini-series actually predates the comic by perhaps a year if we give allowance to production time for an animated episode.
A Real American Hero comics continuity - Marvel
Cobra installed a stronghold in the Trans-Carpathian mountains to create a major foothold in the Eastern European region. When the Cobra ninja Storm Shadow kidnapped Scarlett, he took her to the Silent Castle and held her there. Not long after, Snake-Eyes followed and executed a daring rescue mission. Since then, Cobra Commander had the castle closed down because it reminded him of his vulnerabilities. The castle then came into Destro's possession as part of a bargain between the two men.
Action Force (British) Comics continuity
The castle was called Castle Destro and was located in the Balkans where it had been the base of Destro family line in the Balkans since the time of the Crusades. They ruled from there and selling arms throughout the centuries and regularly shifting alliances. As a result the castle had carried the Swastika and Imperial Eagle emblems in the nineteen thirties and forties, but by the end of the twentieth century it was now bedecked with Cobra serpent symbols.