It looks like a spaceship landed where Nassau Veterans Memorial Coliseum used to sit in the middle of Uniondale. Or maybe a giant radiator.

The aluminum fins that ring the now-black building signal a significant change to the cookie-cutter ’70s-era architecture that the arena had carried for more than four decades. It has what Brett Yormark — CEO of Brooklyn Sports & Entertainment, the company that now manages the Coliseum — calls “curb appeal.”

But the $165 million renovation of the arena goes far deeper than the new facade and the numerous structural improvements to the building. Yormark and his team have re-imagined nearly everything about the Coliseum since it closed in August 2015 — from the now-grand entrance to the type of entertainment you will find there. When it reopens April 5, with a sold-out Billy Joel concert launching the Coliseum’s next chapter, visitors will get a chance to see everything the renovated arena has to offer.

“I know there are a lot of people whose lives have been spent going to the Coliseum,” says Yormark. “But when they walk into the place now for the first time, they won’t recognize it. It’s totally been reinvented . . . I think when you come into the building you’re going to have an incredible ‘wow.’ It was so dated.”

The biggest change, though, may be the programming. “Long Island has been underserved in terms of entertainment,” says Yormark, who led meetings in Los Angeles to explain to agents and booking companies that the Island should be seen as separate from New York City. “Even when the Islanders were finishing up there, they weren’t getting the shows to come.”

The Coliseum has already lined up Barbra Streisand’s first Long Island show since 1963, when she played the tiny Lido Club in Lido Beach. It has booked the only arena show on Metallica’s upcoming “WorldWired” tour of stadiums. And the hottest arena tours of 2017 — including Bruno Mars, The Weeknd and Roger Waters — are all set to stop on Long Island, which, for many years, has been passed over.

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“It’s top of mind to the industry,” Yormark says. “From time to time buildings close, but not a lot open. All eyes are on Long Island, which is terrific.”

Coliseum management plans to make the most of that attention — as it did when it opened Barclays Center in 2012 with a flurry of high-profile sports and entertainment events. Those included eight sold-out concerts from Jay Z and the MTV Video Music Awards (the one where Miley Cyrus twerked) within the first year.

“In many respects, that’s the blueprint for Nassau,” Yormark says. “That first year at Nassau will all be about volume and variety — what makes sense for the market, the building, what’s the appetite for consumers.”

Once consumers come to the Coliseum for the first time, Yormark and his team hope the building and the new amenities will keep them coming back. “We want the Coliseum to have its own identity,” he says. “But we also want there to be consistency in service levels. Whatever we have been able to afford consumers at Barclays Center, we want to afford them the same best-in-class experience out there.”

The changes to the new Coliseum — now officially known as Nassau Veterans Memorial Coliseum Presented by New York Community Bank — are apparent even before you get inside the building.

Beyond the aluminum-finned facade, which SHoP Architects (the Manhattan-based firm that also designed Barclays Center) hopes to conjure thoughts of dune fences at Jones Beach, there is also a new plaza outside the main entrance, with a memorial to veterans at its center. The memorial — made of granite and covered with water, with an eternal flame at the center — will be open to the public whenever there is no event at the arena. And the chain-link fence around the Coliseum has come down.

The main entrance, just off the plaza, is much more dramatic.

“There is a straight view from the main entrance into the bowl,” says Rebecca D’Eloia, senior vice president for development at Forest City Ratner Companies, the Brooklyn-based developer handling both the Coliseum renovation and the neighboring retail and entertainment plaza that will be known as NYCB Live, scheduled to open next summer.The box office is no longer the first thing you see when you walk in. From what is now called The Overlook, you can see the crowd that’s already inside. The box office is to the left of the main entrance and a new beer garden, which will also serve Umberto’s pizza, is to the right.

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The escalators to the event level are still near the middle, but that level has been radically changed. In addition to concession stands, there will be new food carts, the entrance to a new VIP club and a bank of bathrooms. (Bathrooms, often congested at major events, are a big deal in the new Coliseum. The renovation has doubled the number of bathroom fixtures.)

D’Eloia, a Northport native who now lives in Huntington, says the reason they added so much to the event level entrance is because they wanted to relieve some of that crushing overcrowding on the main concourse that patrons have all endured at some point.

“If people understand that they can come in and go down to the event level and get food and drink and a bathroom — and if they have a ticket for the floor, they can get right in to the floor — they will come back to this space,” she says. “It’s all alleviating the congestion that used to be on the concourse.”

Once you get to the concourse, the interior improvements, designed by San Francisco-based firm Gensler, are also immediately noticeable. The glass in the windows and the doors have all been replaced to make the concourse brighter. The red quarry tile floors are light gray terrazzo now. Wood beams give the ceiling some character. The concourse is wider because the permanent concession stands have been pushed back a foot, and it all uses a far subtler palate than Islanders blue and orange.

“There was a lot of visual clutter on the concourse, which happens to buildings over the course of 30 years,” D’Eloia says. “What we did at Barclays and what we want to do here is bring some sanity to all that visual noise . . . it makes people feel that they’re in a really nice environment.”

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The big, blue metal doors that separated the concourse from the seats are also gone, replaced by heavy black curtains across a lighted concrete portal. On the other side of the curtains is another major improvement. By removing a couple of rows of seats, designers created an inner concourse that allows you to move around the arena without walking through rows where people are seated and without going back to the main concourse.

Once you get to your seat, you’ll find that it’s an inch wider than it used to be. (If you’d rather sit on a bar stool, you can buy tickets to perch at a drink rail at the very top of the bowl, where the top two rows of seats used to be.) There is a new scoreboard that can run HD video. The ceiling has been painted black to make concert light shows pop more. And there is now high-density Wi-Fi in the arena, capable of simultaneously handling thousands of users.

“People who thought this was just a paint job are going to walk in and see it’s much, much more than that,” D’Eloia says. “We kept the bones, but we gave it a whole new dress.”

The Coliseum’s executives have high hopes for the future, even if recent years at the arena were disappointing. Yormark says the fact that the Coliseum will be one of only a handful of arenas in America without a major league team as a core tenant isn’t a cause for worry.

“When you look at the building, it’s no different from the Sprint Center in Kansas City, or The Forum in L.A. or The O2 in London,” he says. “The flexibility that not having a core tenant affords us is terrific. We can do the big events, the world-class events that require a couple days to load in and a couple days to load out without having the pressure of hosting an NBA game.”

Yormark says that those kinds of events are on the horizon, adding that opening night on April 5 with Billy Joel shows exactly what is possible.

“It’s going to resonate everywhere and it’s going to be an emotional moment for a lot of people for him to come back and open up this building that has been beloved by fans all over Long Island. We’re just so thrilled and honored that Billy has agreed to do it. It should be one of those nights that you circle on your calendar and remember years from now.”