For nearly a century, the Fulton Street subway complex exuded all the charm of a coal mine -- filled with dingy, gritty hallways, crowded staircases, confusing ramps and inscrutable signage. But the MTA hopes to change that forever as it opens the Fulton Center subway hub Mondayon Broadway in lower Manhattan.

The new main hall -- featuring natural light and space for shops and restaurants -- is designed to guide riders, with a minimum of fuss, to the platforms of nine of the city's main subway lines.

The station will offer wider and less confusing corridors, and mezzanines that separate the flow of entering, leaving and transferring straphangers. And the Dey Street concourse, which opens on Monday as well, will link the Fulton hub's A, C, J, Z, 2, 3, 4 and 5 lines with the R station on Cortlandt Street. As work eventually wraps up on the World Trade Center site, the hub also will connect with the E and 1 subway lines and the New Jersey PATH.

The creation of this long-awaited complex is a story of maddening delays, blown budgets and a grim near-death experience -- when the Great Recession hit. The project was revived only by a shot of federal stimulus cash.

There are lessons from these travails:

Lesson 1: No New Yorker should ever believe the MTA when it talks about costs and completion dates. Fulton Center is crawling to the finish line seven years late and -- at $1.4 billion -- costing almost twice its original estimate.

Lesson 2: Some things are worth having anyway. The MTA says the hub is another Grand Central Terminal -- and this isn't all hype. A full complement of stores and eateries will open in the complex soon. And not only will the hub make transfers at Fulton Street far easier, it should ultimately simplify transfers from the New Jersey ferries.

The hub will also tie downtown into a single, coherent business district. New concourses will link the WTC site on the west with the Financial District on the east. That's crucial as tourism and employment boom in the area.

If the creation of Fulton Center often seemed a trauma without end, the place should quickly prove its value.