Sept. 11, 2009 -- Eight years after 9/11, New York remains the number one target for terrorists in the country. And al Qaeda and al Qaeda-inspired groups retain the ability and the desire to attack, according to public safety and anti-terror officials.
"It is the financial capital of the world, it is the communications capital of the world, and we have been attacked twice successfully," Ray Kelly, commissioner of the New York City Police Department told ABC News. "So it would be a real accomplishment on al Qaeda's part."
And there are new threats. ABC News has learned the NYPD is watching Iranian-backed Hezbollah operatives surveying potential targets as well as home-grown terrorists -- as many as two dozen Islamic extremists in the New York area.
NYPD research has shown that since 2004, 80 percent of terror plotters have been radicalized in the West.
"It is something that we're very much concerned about," Kelly said. These are "Americans who somehow become radicalized and decide to kill their fellow countrymen, innocent countrymen."
To counter the increasingly diverse threat, since 9/11, New York has built an intelligence and counterterrorism operation unprecedented for local law enforcement with 1,000 officers at work across the city and across the world. ABC news was given exclusive access.
The NYPD's critical response surges, when patrol cars converge, without warning, on the site of a potential terrorist target, occur every day, twice a day, somewhere in New York City, say police officials. It's an enormous team effort, 76 patrol cars, one from every police precinct in the city.
And in New York harbor, in the shadow of Wall Street, the NYPD is on the lookout for what it calls the greatest threat to the city today: a nuclear or radiological attack. The NYPD has the only police patrol boats in the world custom-built to detect a nuclear device.
Police officials say the radiation detectors on board are designed to be extremely sensitive, even at high speeds. During exercises, they've been able to pick up radiation sources as far as 40 yards away at speeds in excess of 40 miles an hour.
"We do focus on the shoreline," said Sgt. Carl Root of the NYPD counterterrorism division. "It's going to be there, it could be on a ferry coming over, we don't want to be predictable, we want to go out and see everything."
Hidden in a warehouse in Brooklyn, behind an unmarked door, is the nerve center where agents analyze intelligence from around the world. On staff are 600 expert linguists, including more Arabic speakers than in the CIA and FBI combined.
Intel chief David Cohen was a CIA agent for 35 years.
"The intelligence division's responsibility is to make sure the listening posts are there, that they're listening, and they're reporting, and that they understand what we hear," Cohen said.
Overseas, the NYPD has agents stationed in 10 countries, including in the Middle East, looking for new plots against New York and learning from attacks overseas.
When terrorists attacked hotels in Jakarta this summer, an NYPD detective was on the scene within hours, reporting back to headquarters on the nature of the attack and the risk of it happening here.
NYPD agents abroad also team up with foreign police. In Kabul, the head of the Afghan counterterror police shares what he hears from captured al Qaeda fighters.
"For the new generation of al Qaeda, the big target -- exactly -- it's the United States," said Abdul manan Farahi, director of the Afghan Counterterror Police.
The NYPD's record is encouraging: no successful attack since 9/11. But police say they have foiled more than a dozen plots, including one targeting commuter trains within the last several months.
"To think of the horrific events of 9/11, to think there are people who want to replicate that, is motivation for a lot of us," said Kelly.