Not far from the New York Stock Exchange, a small crowd of tourists stopped to watch as a bomb-sniffing dog checked out a delivery van. The cobblestoned street was blocked by a line of brass cubes with holes that glowed red like the inside of a toaster.
Suddenly an entire section of the street rotated, cobblestones and all. The cubes moved out of the van's way and their holes turned green. The crowd "ahhed" with surprise.
Welcome to New York, a city where every year since 9/11, tighter security has changed the landscape a little bit at a time, more noticeable to the tourists crowding the streets for the holidays than the residents who have been here all along.
"There are so many police," said Jackie Carey, 71, of Wilmington, Del., as she looked over Rockefeller Plaza crowds from the steps of St. Patrick's Cathedral. "There's like about five policemen on the corner. How many policemen does it take for you to get across the street?"
'Not Permitted Beyond This Point'
At Radio City Music Hall, guards check holiday tourists' purses for weapons before the Rockettes' Christmas Spectacular. In Herald Square, new cameras stare down at shoppers.
In rail stations, travelers are bombarded with messages warning them to be on the lookout for suspicious activity. There are poison-gas sensors and radiation detectors, automatic license plate readers and random bag searches in the subways.
The Woolworth Building, a 1913 skyscraper that used to attract hundreds of tourists a day to its ornate lobby, now has a sign at the door saying "Tourists Are Not Permitted Beyond This Point."
Visitors to the Statue of Liberty must go through two separate, airport-style security checkpoints. Taking pictures of the PATH trains that run under the Hudson is illegal. Even the city's architecture is changing: closed "sky lobbies" are replacing ground-level public spaces; vehicle barriers are de rigueur.
At Rockefeller Plaza, concrete barriers emblazoned with "NYPD" blocked part of the streets running through the promenade, which draws thousands of visitors to see its Christmas tree and ice skating rink.
In the subways, train conductors tell passengers, "If you see something, say something." So do posters and ticket machines. Police conduct occasional spot checks, setting up a table in stations and searching travelers' bags at random.
Times Square — now partly transformed into a pedestrian mall — sports wider sidewalks aimed at creating buffer zones around high-profile buildings. Nearly every lamppost now has at least two domed cameras and an antenna for beaming live images to police.
"Cameras, cameras and more cameras," said Robert Jacobs, 30, a visitor from Chicago. "Makes you wonder who's got time to watch it all."
Computers, that's who. In a command center that opened in 2008, software searches constantly for suspicious activity, such as an object that does not move for a long time. The computers can also search for specific shapes and colors, such as a suspect wearing a green jacket. In September, police added 500 more cameras to the system.
Farther south, parts of lower Manhattan are now thickets of vehicle barriers and police checkpoints. Steel plates secured to the ground with thick black chains jut out of the ground in the alleys near Wall Street. Yellow barriers rise and drop silently from the ground at an inspection point near the World Financial Center.
A once-bustling four-lane road that runs past a federal courthouse and the federal jail has been closed to most traffic since 9/11.
At the New York Stock Exchange, a metal fence keeps tourists 30 feet from the building.
Security concerns have also begun to change the look of New York's buildings.
New skycrapers place office workers higher, beyond the reach of a bomb explosion. In One World Trade Center, the 102-story tower under construction at ground zero, the first office floors will be built 200 feet above the ground.
"Now architects are more concerned about the vulnerability of their buildings to say, a truck bomb," said Robert McCrie, a professor of security management at the John Jay College of Criminal Justice.
Most New Yorkers appreciate the security. But some say they miss the days before terrorist plots became a constant worry.
Ilene Zatal, 62, says she used to look forward to buying her monthly Metrocard because of the poetry the city printed on the back of them. She pulled out a stack of her favorites.
"Within five miles of where you live, there are enough strange things to keep you wondering all your life," she said, reading a verse from E.W. Howe. "Wonderful. Before, they used to all say things like that."
Then she pulled out her current card.
"If you see something, say something," it said in Spanish.