In this City, walking down the street you can see people from all over the world. I have never seen any other place in the world with this much ethnic and diversity.
Also walking down the street you will be able to hear people speaking in many different languages. I have never seen another place where I can hear people talking in so many different languages in the same place (restaurant, subway etc.)
New York City's strategic location on the East Coast has made it a world heritage site. By that I mean, people from all over the world started settling in New York City seeking a better life and they have settled into communities with people of their same background. For this reasons you have places such as Little Italy and China Town.
This institution represents any country that wants to be a part of it. And most countries in the world are registered which makes the UN headquarters a sanctuary for world politics. Additionally, any country registered in the UN has the right to visit the UN headquarters regardless of its relationship with the US. For this reason Iranian president comes to New York City and has the right to do so even though Iran has no relations with the US. This truly makes New York City the world center.
New York City holds the most diverse protests and demonstrations in the world. If something wrong is happening around the world, it will somehow b manifested in New York City. For example, when the Ethiopian President was invited to speak at Columbia university. there was a huge protest at the University by Ethiopians and/or US citizens with an Ethiopian background.
The main purpose of a terrorist is to get people's attention to his cause. There has been more terrorist attempts in new York City since 9/11 than any other place in the Western World. The fact that terrorists are using NYC as a destination, proves that NYC would get the attention of the most diverse audience in the world. the 9/11 attacks killed the most diverse group of people than any other terrorist attack in history, therefore the attack made itself felt across the whole world for that.
Broadway shows are really universal. this is because it attracts the greatest talents from all over the world. Anyone in the entertainment business dreams of making it there. this is not just actors, but producers, musicians, dancers etc. So in anyone show you can see talents from all over the world making a contribution somehow.
NYC holds one of the world largest studios for TV shows. Friends is one of the most popular TV shows in the world. Even in Kuwait, almost everyone knows of the show if not seen it. People know it is in New York City and a lot of people get their ideas of what New York City is like through shows such as Friends. in this case the world doesn't just revolve around NYC but 6 friends living in NYC.
Jewish Theological Seminary is arguably the most distinguished institution for studying anything Jewish related.
Union Theological Seminary is also one of the most distinguished institutions for studying religions. Religion is a world wide phenomena and this is the place to study about any religion.
Teachers College is the preeminent Institution for education. TC has helped and continues to create education curriculum for countries all over the world which makes its effects really felt worldwide. It deals directly with many governments Education ministries to develop the education models of that country.