Brussels shut down its subways and schools while the government asked people to stay away from public places because they might be targeted by extremists in a Paris-style attack.
With the lowering of the threat level on Thursday, tourism officials are optimistic that people will return to the Belgian capital, especially with the official opening of the Christmas market on Friday.
Instead of posting updates on where police operations were happening, users tweeted images of cats, including with their paws up, disguised as police snipers and even wearing a bowler hat, the trademark of Rene Magritte, Belgium's greatest surrealist painter.
The police tweeted a picture of a bowl of cat food to thank people for their help and tourism officials are now using images of cats at famous Brussels landmarks in a light-hearted attempt to lure tourists.
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Spokeswoman Inge Van Eycken said there was no precedent for closing the attraction due to terrorism fears and said they are relying on some kitty power, among other measures, to bring visitors back.
"We think some cats will help," she said. Van Eycken said Atomium officials are using an altered image of the 1958 World's Fair structure that replaces the nine distinctive metallic spheres with cat heads, though she stressed they have no plans to import real kitties to the attraction.
"I was very sad and shocked," he said, admitting he had second thoughts about his visit. "This country doesn't deserve something like this."
Patrick Bontick, head of Brussels' tourism office, said he hoped tourists would be reassured that authorities had taken all necessary measures to protect the city.
He said hotels reported a 20 per cent drop in bookings this week and agreed with Van Eycken that cats might be the solution.
"Even in a bad situation, we can also have some humor in Brussels," he said. "We're a surrealistic country," he said, adding he hoped the cats would provide a "friendly" image of the city.