Paris fan zone under 24/7 surveillance during Euro 2016 (The Associated Press)

In the wake of deadly attacks in Paris last November and Brussels this year, Europe is on high alert and authorities are concerned Euro 2016 from June 10-July 10 could be targeted, especially the fan zones where spectators gather to watch games on large screens. Hidalgo says security inside the 130,000-square meters area - the equivalent of 30 soccer fields - set up in Paris will be enforced at all times by 400 privately hired security agents.