Police patrols with bomb-sniffing dogs met passengers at subway exits, directed heavy traffic at the narrow avenue running in front of the building, and mingled with a mob of television camera crews occupying the sidewalks.
There was an additional security checkpoint under a giant umbrella for all employees entering the building.
Stanley Fishman, a financial analyst for Citibank who works in the Citigroup building, told RFE/RL people were obviously more "jittery," but that he wasn't afraid to go to work.
"I faced this kind of heightened security sense before so it's nothing new to me," Fishman said. "But a lot of people are still jittery about it and kind of really anxious about what's going on, how the security situation is unfolding."
Some of the people interviewed expressed skepticism over the terror alert -- issued on 1 August by the U.S. Department of Homeland Security.
They speculated the evidence may not be sufficient for such specific threats. But Fishman said he, for one, was taking the warning seriously.
"I understand the skepticism that a lot of people have, because a lot of the alerts that have been coming out in the past have been very general -- [they tell you to have] a heightened sense of alert, watch out for things -- but people don't really change what they do on a normal basis. But since these alerts came out yesterday, and actually specified not even particular areas but particular buildings -- the Citigroup Center and the New York Stock Exchange -- the people actually are beginning to worry about why this time a particular alert came out for Citigroup," Fishman said.
Viney Kapor is an asset management specialist who works at Deutsche Bank across the street from Citigroup building. He tells RFE/RL that all large financial institutions in New York should always be considered potential targets -- particularly those, like Citigroup, which have partial Saudi ownership.
"A likely target? This is a very good target area -- [the Citigroup building], the [New York] Stock Exchange. I guess anything that exhibits American financial power. Citigroup is almost 6 percent owned by a Saudi prince, right? Terrorists are not big fans of the Saudi royal family, so I guess it makes it a good target to attack Citigroup. Other than that, all major financial institutions -- everything that's big and American and shows some economic might -- seems like a good target whatever their purpose is," Kapor said.
In lower Manhattan, more visible security measures were underway to protect one of the world's most important financial bodies, the New York Stock Exchange. Heavy police trucks guarded the entrance to the financial district and traffic was rerouted away from the area.
Specially armed police officers with stony faces patrolled among the usual mix of tourists and bank employees eating their lunch outside. But despite the heightened security, people appeared to more curious than frightened.
Simona Kruz works at the stock exchange and told RFE/RL that the feeling on 2 August was that it wasn't an average day -- but that people were still calm.
Kruz: [The feeling] was a little different. A little anxiety but not much.
RFE/RL: Did you think to take a day off?
Kruz: No, not at all, that was not an option. My sisters wanted me to take the day off, but that was not an option for me.
RFE/RL: Under what circumstances would you take a day off?
Kruz: Good question. I don't know. My god. I would go by what my gut tells me.
RFE/RL: So what did your gut tell you today?
Kruz: My gut told me to come to work.
Asked about her perception of the frequent terror alerts since 11 September 2001, Kruz said she thinks they are justified.
Kruz: No I don't think, I don't think [that the terror alerts are exaggerated]. I think it's legitimate.
RFE/RL: What do you know about Al-Qaeda?
Kruz: What do I know about it? Not much. All I know is, I wish it would go away.
In a sign of resilience -- on 2 August, at least -- all the major financial market indexes in the United States closed slightly higher.