Heavily-armed police officers patrol Times Square with assault rifles, while others scan the streets from watchtowers, surveillance cameras and helicopters.
They are stopping and questioning people entering the subways.
"I would say that we are as safe as we can be. Are there guarantees in this world? No," NYPD Commissioner Raymond Kelly said.
In an eyewitness news interview, Kelly admitted his security concerns only begin with 9/11.
In the coming days and weeks the NYPD will be stretched to the limit protecting world leaders at the United Nations General Assembly; models, fashion writers and designers here for Fashion Week; the U.S.S. New York on the West Side; and the city's synagogues during the high Jewish holy days.
On top of that, twenty-five thousand people are expected for the U.S. Open on 9/11, while the New York Mets will play at Citi-Field.
That's all in addition to the solemn ceremony at ground zero.
"A day like 9/11 may give people some cause for concern, but we are in my judgment taking care of business and doing what has to be done to protect the city," Kelly said.
Kelly says the city's subway system and the commuter rail lines are the most challenging terrorist targets to defend.
While quick-thinking helped foil the bombing attempt in Times Square, more than a year later, Kelly is still troubled by it.
"We've devoted a lot of effort, a lot of money, a lot of resources to protecting the city and this individual drives right on in on a Saturday night and attempted to detonate a bomb. So, it's a dangerous world," Kelly said.