America's most famous piece of self-built architecture.

The legendary building that needed ghostly approval before being built.

One of Antoni Gaudí's least-visited works, an homage to Catalan patrimony that mixes neo-Gothic with Modernista forms.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

The unexpectedly beloved remnants of a controversial thermal power plant.

Catacombs turned marketplace.