A crowd of frustrated tourists looked longingly through the maze of metal barriers lining the River Seine, where Notre Dame Cathedral and other Parisian landmarks remained just out of reach.

“We don’t have a code,” said a Mexican woman, watching as others with the necessary QR security codes passed through a police checkpoint with a confirming beep.

Down by the Eiffel Tower, a tired couple with large suitcases had just been told by a French gendarme to take a detour, as the area was closed.

Paris is gearing up for a unique Olympic opening ceremony this Friday evening, which will feature athletes parading on gleaming barges through the heart of the city. This event has prompted the largest peacetime security deployment in French history, with up to 75,000 police, soldiers, and private security personnel stationed in Paris at any time.

In preparation, roads and metro stations have been shut down, 44,000 barriers have been erected, and a detailed QR code system has been implemented for locals and others needing access to the Seine and its islands.

These measures have caused notable disruptions. “I’m a little bit worried. I’ve never seen it so calm. Ninety percent of clients have gone,” said Omar Benabdallah, a waiter observing the empty tables on the Île de la Cité.

Despite the inconvenience, French officials assure that the disruption will be short-lived, with most barriers being removed after the opening ceremony. Gen. Lionel Catar, overseeing 5,500 French troops in the city, described the security effort as “exceptional” but noted that it builds upon France's existing Opération Sentinelle, a response to past attacks by Islamist extremists.

The operation includes demining teams, dog units, anti-drone systems, radars, and divers patrolling the Seine. The decision to base the operational headquarters at the École Militaire near the Eiffel Tower, rather than on the city's outskirts, came from UK police advice based on their experience with the 2012 London Olympics. This move aims to keep the headquarters close to both politicians and police.

About 250 British officers and 50 police dogs will be in Paris for the Games, among 1,750 international officers from countries like Spain, Germany, South Korea, and Qatar. Chief Superintendent Matt Lawler of the UK National Police Coordination Centre highlighted the deployment of UK officers as a first in major events abroad.

French and UK military forces are also collaborating on anti-drone technology, especially for the opening ceremony. While no specific threats have been identified, French officials are wary of potential "militarised terrorism" and cyber-attacks targeting ticketing systems and other critical infrastructure.

France has expressed frustration over what it sees as a Russian-backed disinformation campaign exaggerating security concerns. Interior Minister Gerald Darmanin criticized this interference and expressed hope for an Olympic truce.

On Tuesday, French police arrested a Russian individual suspected of planning disruptive acts during the Games. Earlier, an elite French police unit conducted a rehearsal for a hostage situation on a bus, simulating a rescue operation amid gunfire and explosions.

“We’re feeling impatient. We’ve spent more than two years preparing for these Games. Let’s hope we will not have to take any action,” said the unit’s commander, Simon Riondet.