SAN FRANCISCO (KPIX 5) – It is both the most ambitious and risky project San Francisco has seen in modern times.

A $2.19 billion transit center, complete with a four-block long rooftop park, a massive shopping mall and an underground train station, all in the heart of downtown.

“This is a place that is going to be happening – believe me,” said Mohammed Nuru of the San Francisco Department of Public Works.

Scott Boule of the Transbay Authority told KPIX 5 the project is “larger than Union Square, South Park and Yerba Buena combined.”

The project also includes a suspension bridge to get buses on and off the Bay Bridge without going through traffic, along with an 800 seat roof top amphitheater for concerts and performances and a half mile of jogging tracks

Boule said the project would include 13 different gardens, which means lifting in 690 trees from all around the world, up some 60 feet.

But like all things San Francisco, it comes with controversy.

For starters, the $700 million train station being built in the basement isn’t likely to be connected to any railroad for years to come.

“Before then – we will have buses running here,” Nuru said.

There are also lawsuits involving the Millennium Tower next door, whose builder claims is sinking in part because of all the digging on the project.

“It is going to be the most expensive ongoing problem the city has,” Supervisor Aaron Peskin told KPIX 5. “This was supposed to pay for itself. Now we are hearing that it is going to cost $10 million a year.”

Nuru said, “All these places obviously cost money to maintain.”

A good part of that money they are banking to come from tenants in the massive mall, at a time when brick and mortar is shrinking.

Matier: “You have four blocks of shops to rent out.”

Nuru: “To make it work, you have to bring everything together, and it’s a new experience for us, but we believe we’re going to make it work.”

If all goes according to plan, the new center would be the terminal for the high-speed rail to Los Angeles, bringing in hundreds of thousands of passengers.