Inside Silverstein’s 4 World Trade Center

Five years in the making, the minimalist 72-story, 978-foot tower - the fourth tallest in the World Trade Center complex - is made up of a 75-foot tall "podium" housing retail and transit infrastructure, plus 2.3 million square feet of office space.This weekend, observers got a chance to tour the lobby and the 42nd floor of the building as part of the 11th annual Open House New York weekend, when dozens of architects, developers, and cultural and religious institutions flung open their doors to the curious public.About 30 observers, led by a Silverstein employee, donned hard hats and neon yellow vests, first scoping out the lobby (no photos allowed!) and then riding a rickety construction elevator up high above the city.Designed by Pritzker Prize-winning architect Fumihiko Maki, the tower features a coated glass exterior that echoes the surrounding buildings and the sky, creating a constantly changing façade.Maki replicated this idea in the 47-foot-high lobby, using polished black granite that reflects the 9/11 Memorial across the street.

While the lobby is almost complete, the 42nd floor is still a parallelogram-shaped concrete box, with marketing materials set up on easels against one wall, and another wall curiously bearing graffiti that says, "Honey Boo Boo." But most visitors were captivated by the views - New Jersey on one side, 1 World Trade Center and 7 World Trade Center on the other, and to the north an expanse of Manhattan spread like a smog-colored blanket at their feet.

The floor plates - 44,000 square feet on the seventh through 46th floors, and 34,000 square feet on the 48th through 63rd floors - were designed to leave vast column-free expanses to allow for the most flexible and efficient use of office space. Silverstein estimated that the configuration would allow tenants to rent about 10 to 15 percent less office space than they would in other buildings.

Asking rents start in the mid-$70s per square foot, but drop to the low-$60s per foot when tax abatements, energy discounts and space efficiencies are factored in, according to the marketing materials.

So far, the Port Authority of New York and New Jersey has signed on to anchor the tower, taking 600,000 square feet of space. Facebook, Nielsen Media Research and an unidentified law firm have also checked out the building, brokers told The Real Deal last month.