Doctor Chaotica's Fortress of Doom
The Fortress of Doom was the name of Doctor Chaotica's base of operations, located on planet X. It also housed his death ray, which he used in his attempts to conquer Earth.
The Fortress of Doom was part of Tom Paris' The Adventures of Captain Proton holo-programs. Accessible by a drawbridge, the fortess contained many of Chaotica's evil inventions and henchmen, and was protected by a Lightning shield, both of which made infiltration by even Captain Proton quite difficult.
The Fortress of Doom, after taking damage from retaliatory attacks by photonic lifeforms.
The lightning shield failed to protect the fortress, allowing it to take heavy damage when the appearance of photonic lifeforms caused the program to be left on continuously, setting off a war between them and Chaotica. (VOY: "Bride of Chaotica!")