A once grand hotel now sits eerily abandoned in the Catalan countryside outside Barcelona.

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

Along the pavement of this neighborhood in Madrid are quotes from famous authors.

This 18th-century project to build the world's tallest gravity dam was never completed.