>>63829779 (OP)>hiding a Star Destroyer under an apartment complexYou joke, but this was literally an actual plot in Star Wars EU. When the Super Star Destroyers (the Executor from Empire Strikes Back/Return of the Jedi being one) entered service, Palpatine had one, the Lusankya, hidden away on Coruscant, for use as his personal getaway vehicle in the event that his reign was threatened.
How did they do it? A portion of the city was first demolished, the ship was buried in a specially-built cradle, and then the city was subsequently rebuilt over it, with Palpatine using his Force powers/mass executions of the workers to keep it a secret.
The ship remained hidden away until the Fall of Coruscant several years after Palpatine's death where the lead Imperial glownigger Ysanne Isard used it to escape by literally blasting the ship through the cityscape it was buried under, killing millions of people in the process.