New York City

New York is the most populous city in the United States, and the center of the New York metropolitan area, which is one of the most populous metropolitan areas in the world. A leading global city, New York exerts a powerful influence over global commerce, finance, media, culture, art, fashion, research, education, and entertainment. As host of the United Nations Headquarters, it is also an important center for international affairs. The city is often referred to as New York City or the City of New York to distinguish it from the state of New York, of which it is a part.

Percy Jackson and the Olympians
The title hero, Percy Jackson, lives in NYC and attends Camp Half-Blood, located on Long Island. Olympus is located on the 600th floor of the Empire State Building. A majority of the series takes place here.

Trivia

 * While not mentioned in the series itself the borough Manhattan, where the Olympians live, is avoided by certain other groups