From PE teacher to gym mogul: third Železná koule gym opens in Prague

The founder of Prague’s Železná koule (“Iron Ball”) gym chain, Michal “Radar” Vratný, has opened his third Prague location — this time in the business district of Karlín, inside the renovated Dunaj House building next to the Hilton hotel. The new gym is the chain’s biggest and most expensive to date, with an investment of around 30 million kroner.

Vratný, a well-known figure on the Czech startup and fitness scene, had long been searching for a suitable space in Karlín, but nothing seemed to fit. He initially ignored an offer from the agency Dejsiprostor.cz, assuming it was just another “hipster” loft with exposed brickwork. But as soon as he saw the former premises of an Asian restaurant, he knew it was the right fit for Železná koule.

The new gym covers 600 square metres and keeps the chain’s signature industrial look: rebar jutting from the walls, battered concrete partitions and walls cracked as if by an explosion — all of it entirely intentional. The building’s owner covered part of the renovation costs, and Vratný and his partners are gradually paying the investment back through rent.

A curious detail: Dunaj House itself, like the entire Riverside Karlín complex, belongs to the Austrian company CA Immo — but it is currently being bought by Czech businessman Radomír Lapčík, owner of the group built around Trinity Bank, for 7 billion kroner. The antitrust office approved the deal last week.

Železná koule was conceived from the start as an honest gym without high-tech equipment, a place where people come to sweat rather than pose for social media — the chain began in the worn-down premises of a former print shop near Národní třída. Vratný says that if he’d had the money back then, he would have made even his first gym more presentable — but he could only afford that now.

Today the chain has three locations in Prague: in Strašnice, in Smíchov and now in Karlín. There used to also be a branch in Holešovice, which spun off to become independent, while the location near Národní třída has since closed. Železná koule’s business model differs from a classic gym: you can’t just drop in for a workout — only group classes for registered members or the long-term Amazing 6 and Amazing 12 programmes are available. Over 15 years, more than 20,000 people have trained with the chain.

The interior of the new Karlín gym was designed by architect Petr Vojáček of studio N78o — a longtime student of Vratný’s who has trained with him for years. The first wave of Amazing programmes at the new gym starts on 31 August, and there are already no places left — the gym filled up with clients just a few days after opening.