The High Line on Manhattan's West Side is the inspiration for a proposed underground park called the Lowline, and a new exhibit shows what the Lowline would look like.

The Lowline has gone from renderings to reality. Well, sort of.

The idea of transforming a closed trolley terminal under the Lower East Side into a subterrannean park is being tested, with a model built in a nearby building.  

"This is a functional lab in which we can see what we are able to do in terms of irrigating light and in terms of what we can grow. But it's also an outward-facing one," said Lowline co-founder James Ramsey. "So this is intended to give people a sense of what's possible."

Ramsey proposed the underground park six years ago after seeing the football-field-sized space, vacant since 1948.

"It's not every day that you find 60,000 square feet in New York, right?" Ramsey said.

"In a city really defined by scarcity, we need to think more creatively about how we use and reuse the spaces that we already have built," said Lowline co-founder Dan Barasch.

That's the kind of thinking led to the Lowline's inverse, the wildly popular High Line, built on an old elevated rail line.

The Lowline Lab envisions how an underrgound high line would look, showing how to brighten an underground space next to subway tracks.

"It's futuristic for sure, but this is not a magic trick. This is real math and science that enables us to do this," Ramsey said.

An MTA video encouraged big ideas for the space, which the agency owns.

The MTA has not taken a stand on the Lowline, saying only that the project would need approval by the city's Economic Development Corporation. The EDC did not comment either.

The Lowline's supporters say local officials back their plan.

"I think the Lowline is absolutely not only possible but actually inevitable, because it allows the city to imagine an entirely new use for the underground," Barasch said.

Some riders at the Essex Street station, next to the Lowline space, have their doubts.

"The first time that I've heard about this idea, but I think it is crazy," said one rider.

Fortunately, you can judge for yourself.

The Lowline Lab will be open to the public on Saturdays and Sundays from noon to 6 p.m. through March 2016.