Developers of the renovated Nassau Coliseum have unveiled details of a nearly 20-foot long memorial honoring U.S. veterans that will be erected outside the Uniondale arena.

The dark granite oval memorial will measure 19 ½ feet by 16 ½ feet and feature water flowing along its surface. In the center, emerging from the water, is an eternal flame.

“The contrasting elements in constant movement, set within a simple, yet dramatic form, will provide a stunning tribute to our nation’s veterans for decades to come,” said Bruce Ratner, executive chairman of Forest City Ratner Companies, the project’s lead developer.

Nassau County Executive Edward Mangano said the arena “will have a respectful plaza dedicated to honoring all of our county’s hometown heroes.”

The monument will be located on the southeast corner of the Coliseum plaza, between the box office and the Long Island Marriott. National Grid will donate the gas supply for the flame, officials said.

The Nassau Veterans Memorial Coliseum, opened in 1972, was built at Mitchel Field on a former Army and Air Force base.

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But some veterans have complained that not enough was done to honor members of the Armed Forces. The primary veterans tribute has been a plaque affixed to a boulder on a grassy patch near the site of the new memorial.

Frank Salamino, quartermaster for VFW Post 2736 in East Meadow, welcomed the new memorial.

“It’s better than nothing,” said Salamino. “Anything to honor veterans is a good idea.”

Last week, Brooklyn Sports & Entertainment, the company overseeing the renovation, announced that the arena will be renamed the “Nassau Veterans Memorial Coliseum Presented By New York Community Bank” when it reopens in April after 18 months of renovations.

New York Community Bank purchased the naming rights to the arena and the retail and entertainment district — which will be called “NYCB Live” — for an undisclosed sum.

Ratner is spending $260.5 million to renovate and downsize the Coliseum and construct an adjacent retail and entertainment plaza. The cost of the memorial project was not disclosed.

The Coliseum closed in August 2015 and renovations began that October. The arena will reopen April 5 with a Billy Joel concert. Construction of the retail plaza has not begun.