After 10 years of baiting the “Calatrasaurus” — architect Santiago Calatrava’s years-behind-schedule, billions-of-dollars-over-budget World Trade Center Transportation Hub — I finally visited the belly of the beast.

I strolled through the football field-length Oculus, which I’d ridiculed as “elephantine excess” and likened to an “LOL-ugly” sci-fi movie horror, and which The New York Times’ architectural critic gently termed a “kitsch stegosaurus.”

And — surprise! — the Oculus, which will partially open to the public the first week in March, is as functionally vapid inside as it is outside. It’s a void in search of a purpose other than to connect a bunch of subway and pedestrian corridors and concourses with one another.

The ribs rising to a 22-foot-wide skyline frame an impressive ovoid space, for sure. How could a white marble floor 392 feet long, 144 feet wide and a ceiling 160 feet high at its apex not be impressive?

But what will the public find on the vast, 56,448-square-foot floor?

Nothing. Not a seat. No newsstands or snack concessions. No central information kiosk like the one that provides a focus to the main hall of Grand Central Terminal, to which Calatrava and the Port Authority presumptuously compare the hub.

Why? An empty floor was Calatrava’s idea. But also, the PA plans to pimp out the Oculus as an event venue, and any installations would get in the way. (How transit riders will make their way around weddings and corporate celebrations remains to be explained.)

At the notoriously crowded, 16-acre WTC site where every square inch is precious, the Oculus has free rein to stretch and preen out of all proportion to its function.

The Oculus is not the “eighth wonder of the world,” as Port Authority capital projects chief Steve Plate called it during Friday’s walk-through. It might one day be regarded as a “civic monument,” as Calatrava himself termed it on Friday.

For all the project’s faults, first-time visitors will ooh and aah over the white-painted steel ribs and vertical window panes that frame an unthreatening cathedral of light. Unlike the fishbone exterior, the innards possess at least some of the “lyrical buoyancy” I found in the original 2005 design before cost-cutting snipped away its most gracious elements.

But the March opening will allow access only from PATH platforms to the west. Commuters will find a lifeless void until 75,000 square feet of stores around its perimeter on two levels open when leaseholder Westfield gets around to it and until myriad under-construction elevators and escalators connect with subway lines and nearby office buildings.

The passageways, to open later this year, will let you walk underground all the way from Brookfield Place in Battery Park City to William Street via the MTA’s Fulton Center — although, except in a blizzard, most of us would rather enjoy the sights and sounds of the streets.

Recriminations over the hub’s epic construction saga and $4.4 billion cost won’t likely vanish even after it’s fully functional.

As a reminder, Port Authority executive director Patrick Foye — who’s called his own agency’s pet project a “boondoggle” — gave us the following remarkable statement:

“The cost of projects, big and small, matters — a lot. Whether due to unforeseen conditions, errors or misconduct, cost overruns consume precious resources and undermine public confidence.”

So does a monument to an architect’s ego and a public agency’s institutional vainglory.