Inside the new $550k Straight Blast Gym, John Kavanagh's famous fight club that's home to Conor McGregor

Kavanagh has been lauded as one of the top mixed martial arts coaches in the world, and is known for his work developing the talents of the former two-weight UFC champion Conor McGregor, the highly-rated Bellator MMA featherweight James Gallagher, and the Bare Knuckle Fighting Championship brawler Artem Lobov.

Read more: MMA firm Bellator wants to exploit a market that has been largely neglected by the UFC, and Conor McGregor's coach John Kavanagh is a crucial part of the plan

Though many professional athletes train there, it is open to anybody who wants to learn mixed martial arts or simply get fit.

One photo frame immortalizes one of Kavanagh's most iconic nights as a coach.

At the O2 in Dublin (now called the 3Arena) in 2014, Kavanagh looked after four athletes at a UFC Fight Night event. While McGregor beat Diego Brandao in the very first round, Kavanagh oversaw four victories (all stoppages), with three of his athletes receiving win bonuses.

The plaque here says: "Straight Blast Gym is the first and only European team ever to achieve this."

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With 16,000 sq. ft., there are plenty of dedicated areas to train, including a large space for jiu jitsu and ground work, above, which is next to a full-size MMA Octagon. "An MMA gym is pretty simple," Kavanagh told Business Insider. "You need large, open spaces that you can put down mats."

Mats, he said, are usually the biggest investment.

He said the only thing his fight club needs is open space and to be warm, clean, and dry.

Kavanagh added it was the opposite to his first gym, nicknamed "The Shed," which was "cold, wet, and stinking."

It's here where he will oversee sparring involving the top names at his gym like McGregor, Gallagher, and Lobov.

The graphic behind the Octagon shows a crowd, which is there to better simulate what a fight night experience would be like. You can also see lockers to the right side of the Octagon, the SBG logo on the mat, as well as Monster Energy branding.

There is a lot of Monster at SBG, but tea and coffee are also on offer.

When Business Insider visited on Tuesday, Kavanagh told us the place still looked like a building site only four weeks ago.

"We put the hard months in, threw a lot of money at it, and we were looking at it, thinking, 'It's not even close yet,'" he said. "I might have been a bit naive going from 8,000 sq. ft. to 16,000 sq. ft. We doubled in size but doubled the problems. But we kept at it, and here we are now."

Opposite the Octagon and behind some SBG balloons still standing from the gym's launch, there is also a logo for McGregor Fast, the fighter's extreme performance training plan online.

Kavanagh tweeted a photo of a recent occasion alongside the caption "Legends."

McGregor was in the foreground of the shot in the SBG Octagon, with historic heavyweight boxers like Rocky Marciano and Sonny Liston in the artwork behind the balcony above him.

Behind it lies a photo of Muhammad Ali knocking down Sonny Liston in the first minute of the first round of their heavyweight championship rematch in 1965.

He told Business Insider if and when there are criticisms of MMA from Irish politicians, he asks if they have ever been in a fight gym, and that anybody in the political arena has an open invitation at SBG.

"If I see anything negative online I usually contact that politician directly and say, 'Look, your impression may be from seeing glimpses on YouTube but have you ever visited a gym?' Invariably the answer is no. So I say, 'Come down.' Any politician who has done that, and it's only been a handful, they've all been pleasantly surprised," he said.

"Not everybody wants to play team sports, not everybody wants to kick a ball. But some people like punching, kicking, and grappling. I did. And so do a lot of other people. There's ordinary mums, dads, kids, and people just wanting to be part of a community, get healthy, and be fit, strong, and all those good things."

"If you had visited me in my last gym, or any of my last eight gyms, I would be slow to show you the changing rooms. They were always a source of embarrassment. The main training areas were fine and that is what's important but I wanted the bathrooms in my final gym to be a bit special."

Kavanagh teamed up with a firm that renovate five-star hotels to build them.

"I got really lucky with that connection," he said. You can see the men's changing room and showers above.

"There's a lot of strong evidence to suggest it will help recovery and there's actually evidence it's a testosterone booster, a human growth booster … a lot of good stuff. I like to jump in before training, it limbers me up. And there's team-building going on," he said. "At the end of a session we'll go in and yap away. It's a nice bonus."

There is also an SBG-branded Street Fighter 2 video arcade.

The way Kavanagh runs things, there will likely be even more to come.