Travelers begin at the last surviving gate of Barcelona's medieval wall, right beside the Royal Shipyards. Every other city gate was demolished in 1854 - this one survived because it stood on active military land. The app reveals why, and what saved it.

A grand former customs house covered in oversized stone eagles and mythical beasts. Travelers read a single word carved across its facade to solve this step's puzzle - a small detail that reveals a real linguistic tension in the building's history.

A 60-metre column crowned by a bronze statue of Columbus, built for the 1888 Universal Exposition. Travelers circle the base counting carved animals, uncover the true builder's forgotten signature, decode a Roman-numeral plaque, and finish by tracing exactly where the statue's famous pointing arm really points.