A riverfront park the city spruced up with $4 million in taxpayer money is now a virtual wasteland.

The main entrance to Bridge Park in the Bronx, a greenway that runs under the Washington Bridge along the Harlem River, was gated off for months and only reopened Thursday, a day after The Post asked about it being closed.

But inside was no oasis.

The Post found benches so overgrown with vines that there was no place to sit and graffiti marring a path and a water foundation.

There was also a sign warning of sewage discharge that was riddled with bullet holes.

The lack of maintenance could be seen in leaves and tree needles that lined a walking and biking path.

The only visitors were two men walking their pitbulls.

That’s a far cry from the photos on the Parks Department web site that show pristine benches and neatly manicured walkways.

Just four years ago, officials touted the newly renovated space in a ribbon-cutting ceremony.

“Thanks to this project, Bridge Park will now serve as the ‘gateway to the greenway’ and will provide this community with another way to get fit and stay healthy, or simply take in the beautiful views,” said NYC Parks Commissioner Mitchell Silver said at the time.

Work included new seating, a bicycle rack, drinking fountains and new trees and shrubs between the park and the adjacent Metro-North Railroad tracks.

The renovations were paid for with money allocated by Bronx Borough President Ruben Diaz Jr., City Councilwoman Vanessa Gibbson, the mayor’s office and a federal grant, according to the Parks Department.

The Parks Department said the gate was put up in June to stop unauthorized vehicles from entering.

A second entrance to the park, obscured in the River Park Towers housing complex to the north, had been kept open.

The NYPD said it had no reports of crime at the park this year.

“Our team works hard to keep Bridge Park clean, which includes regular maintenance on the park’s facilities and amenities,” said Department spokesman Dan Kastanis, who on Friday added that the agency would inspect the park this weekend and make any necessary repairs.