Thousands of people marched on Saturday in the Sicilian city of Messina to protest against the construction of the world’s largest suspension bridge, which would link the Italian mainland with Sicily in a massive 13.5-billion-euro ($15.5 billion) infrastructure project.

Protesters staunchly oppose the gigantic project, which has been long delayed by debates over its scale, earthquake threats, environmental impact and the specter of mafia interference.

Organizers said 10,000 people participated in the protest, pledging they would bloc the construction works.

The Strait of Messina Bridge has been presented as “the biggest infrastructure project in the West,” by its main sponsor, Transport Minister Matteo Salvini, after an interministerial committee with oversight of strategic public investments approved the project earlier this week.

Salvini cited studies showing the project will create 120,000 jobs a year and accelerate growth in economically lagging southern Italy, as billions more in investments are made in roads and other infrastructure projects accompanying the bridge.

Opponents, however, complain that the bridge – with its massive environmental impact – would only damage the local population, with at least 500 families expected to be forced to leave their houses in the area where the construction works will start.

Preliminary work could begin between late September and early October, once Italy’s court of audit signs off, with construction expected to start next year. Despite bureaucratic delays, the bridge is expected to be completed between 2032-2033.

“The Strait of Messina can't be touched,” protesters screamed as they took to the central streets of Messina, holding a red banner with the slogan: “No Ponte” (No Bridge).

The Strait of Messina Bridge would measure nearly 3.7 kilometers (2.2 miles), with the suspended span reaching 3.3 kilometers (more than 2 miles), surpassing Turkey’s Canakkale Bridge, currently the longest, by 1,277 meters (4,189 feet).

The project has been approved and canceled multiple times since the Italian government first solicited proposals in 1969. Premier Giorgia Meloni’s administration revived the project in 2023, and this marks the furthest stage the ambitious project— first envisioned by the Romans — has ever reached.

With three car lanes in each direction flanked by a double-track railway, the bridge would have the capacity to carry 6,000 cars an hour and 200 trains a day — reducing the time to cross the strait by ferry from up to 100 minutes to 10 minutes by car. Trains will save 2 1/2 hours in transit time, Salvini said.

The project could also provide a boost to Italy’s commitment to raise defense spending to 5% of GDP targeted by NATO, as the government has indicated it would classify the bridge as defense-related, helping it to meet a 1.5% security component.

Italy argues that the bridge would form a strategic corridor for rapid troop movements and equipment deployment to NATO’s southern flanks, qualifying it as a “security-enhancing infrastructure.”

However, environmental groups have lodged complaints with the EU, citing concerns that the project will impact migratory birds, noting that environmental studies had not demonstrated that the project is a public imperative and that any environmental damage would be offset.

Italy’s president also insisted that the project remain subject to anti-mafia legislation that applies to all large-scale infrastructure projects in Italy out of concerns that the ad-hoc arrangement would weaken controls.

Salvini pledged that keeping organized crime out of the project was top priority.