Forest grows in downtown Manhattan.

Without question, the side-walks in front of 101 Warren Street will be buzzing with activity.

Under development in Tribeca just two blocks from reemerging Ground Zero, 101 Warren will add to the bustle of downtown by housing commercial giants such as Whole Food and Barnes & Noble in its base, along with several restaurants, a gym and spa and other commercial entities sure to spice up life at the bottom of the island.

Given the amount of action sure to take place below, it might seem hard to believe that when developer, Edward J. Minskoff, talks about what life will be like for residents of the 228 condominiums and 163 apartments that will rise 35 stories above the ruckus, he uses words like "serenity."

He does this due to the presence of another entity on the site: a fifth-floor atrium, designed by landscape architect, Thomas Balsley, that will contain 101 Austrian pine trees.

"[The Atrium Forest] infuses the entire building with its energy and serenity," said Minskoff in a statement. "The Atrium is the soul of 101 Warren Street."

When Balsley was called upon to design an atrium for 101 Warren, he said he considered the merits of both the city and the country.

"I want nothing more with my work than to bring people back into the cities from the suburbs. I feel like that's such an important thing," Balsley said. "At the same time, the city can be a difficult place to clear your mind, to really be at peace and have a calming experience. [At 101 Warren] I wanted people to feel the way they can in a forest."

Balsley liked the idea of using pine trees for several reasons. First, they stay green all year round and never lose their needles, thus offering visual protection from the surrounding buildings in all seasons. Second, pines tend to lose their lower limbs as they grow taller, thereby creating an effect much like being in a cathedral, or other building with high ceilings. Lastly, Balsley said pines were simply the most practical choice.

"Pines grow quickly, so you can have a mature forest there in a short period of time," he said.

To speed nature along, Balsley is not planting, but importing his trees from Austria. Some of these trees are already over 20-feet tall. After careful research and discussions with arborists and experts at many nurseries, Balsley concluded that the pines from Austria were best suited to surviving on his elevated terrace.

"Basically, I had a list of trees that I thought would work well in the space aesthetically," Balsley said. "From there, you have to consider what trees can survive living on a roof in New York City ... Especially when you consider the building's proximity to the [Hudson] river. The trees need to be able to survive a storm blowing off the water."