Silverstein said he sees the commercial real estate market as "strong." And he thinks that with a lot of aging office buildings in New York City, his investment will pay off.
"The truth of the matter is, today's large corporations need technology and you can only get the technology in brand-new buildings," he said.
He also isn't concerned about the effect of high taxes driving the wealthy out of the area. According to a recent Wall Street Journal op-ed by conservative economists Arthur Laffer and Stephen Moore, the new tax bill will cause a net 800,000 people to move out of New York and California over the next three years.
"There are people who will be leaving by virtue of the tax hit that they're taking due to the tax change," Silverstein said. "But I'd say the overwhelming number will probably not. Most of them will end up staying, as we've seen in previous years when issues of this nature surfaced."
So far, nearly 80 percent of the space is leased at 1 World Trade Center, while 4 World Trade Center is 100 percent leased.
The completion of this latest phase at the site comes as New York's financial district is experiencing a revival.
The commercial vacancy rate is below 10 percent and residents are also moving to the area. About 61,000 people live in the area, more than ever before.
Tourism is also booming, with nearly 14 million coming to the area in 2017 to visit Wall Street and the 9/11 Memorial.
Urban planner Alexandros Washburn, a former chief urban designer for New York City, said the renaissance since the terror attacks has been a "miracle."
"The transformation has been total," he said on "Power Lunch."
"We honestly didn't know if downtown was going to make it after 9/11. And then after the financial crash, that was more of a hit," added Washburn, a professor at Stevens Institute of Technology.
"But every time it's comes back with a better balance, more richness in the types of buildings that are here, the types of open spaces."
— CNBC's Bob Pisani and Kerima Greene contributed to this report.