The Maeslantkering, recognized as the world’s largest movable metal structure, is one of humanity’s most remarkable engineering achievements, designed to protect the Netherlands from catastrophic flooding. Located near Hoek van Holland, close to Rotterdam, this massive storm surge barrier forms a critical part of the country’s famous Delta Works flood-defense system.
Completed in 1997, the Maeslantkering was built to shield the densely populated Rhine–Meuse–Scheldt delta from North Sea storm surges. The structure consists of two enormous hollow steel arms, each as long as the Eiffel Tower, connected to a central pivot. When fully closed, the barrier spans the entire waterway, sealing off Rotterdam’s harbor from rising sea levels.
What makes the Maeslantkering truly extraordinary is its mobility. Under normal conditions, the arms rest open along the riverbanks, allowing uninterrupted shipping traffic to one of the world’s busiest ports. When severe storms threaten, a fully automated computer system activates the barrier, filling the arms with water so they rotate and sink into position, forming a solid metal wall against the sea.
Each moving arm weighs thousands of tons, yet the entire system operates with remarkable precision. Engineers designed it to function almost autonomously, making it one of the most advanced examples of large-scale movable infrastructure ever built. Despite its immense size, the barrier has only been closed a handful of times, each event serving as a real-world demonstration of its reliability.
