Paris has Notre Dame, Rome the Colosseum. This brand new mini-city takes pride in a different kind of monument—a tangle of rusting metal that was once one of the region's biggest iron and steel mills.

In Luxembourg, one of the European Union's smallest nations, the government and developers have spent more than €1 billion ($1.3 billion) and counting to build a vast complex of apartments and office buildings around the silent, towering blast furnaces of the Belval mill. The development, built on once-polluted land next to the French border, is pitched as "urban living" to house 7,000 residents and host 25,000 workers.