Location from Percy Jackson by Rick Riordan
The mortal entrance to Mount Olympus — take the elevator to the 600th floor and try not to look surprised when the security guard asks if you're visiting the gods.
The Empire State Building is the most important building in the Riordanverse because it's the gateway to Mount Olympus. The 600th floor — which doesn't exist on the building's official plans or in any elevator's button panel — opens onto the divine realm through a special key card held by a bored security guard who pretends not to see the occasional teenage demigod stumbling through his lobby covered in monster dust. During the Battle of Manhattan, Percy's forces fortified it as the gods' front door, fighting Titan soldiers up the stairwells while Kronos marched through Midtown toward the entrance.
The real Empire State Building in Manhattan — except the lobby has a bored security guard who holds the key to the mythological 600th floor. Press the button and the elevator takes you to Olympus.
Also known as: the Empire State Building, ESB