Can you go inside NYSE?

Can you actually enter the physical premises of the New York Stock Exchange (NYSE)? I understand it's a prestigious institution that handles billions of dollars worth of trades every day, but are visitors allowed inside? If so, what's the process like to gain access? Do you need special permissions or credentials? Are there certain areas that are restricted or off-limits to the general public? I'm quite intrigued by the inner workings of such a historic and influential financial institution.