Travelers will find a striking stone building with twin domed towers. Above the entrance sits a large clock that ruled Barcelona's official time from 1891 to 1926. The app reveals the story and a puzzle based on the inscription beneath the clock face.

Also known as the Casa dels Paraigües, this Modernista building is covered in cast-iron umbrellas, painted panels, and Egyptian-style columns. A wrought-iron dragon reaches out over the street from its corner, holding a lantern above a hidden second object. Travelers solve a puzzle based on what hangs beneath it.

A grand nineteenth-century square lined with palms and arcades. Two ornate lamp posts flanking the central fountain were the very first commission the city of Barcelona ever paid a young Antoni Gaudí to design, in 1878. Travelers count the arms on the lamps to solve the step.

Travelers stand between the City Hall and the Palau de la Generalitat, facing each other across Barcelona's ancient Roman forum. A short detour to the original 1399 Gothic doorway on the side street reveals a carved winged figure above the entrance, the answer to this step's puzzle.

A narrow, easy-to-miss street marks the highest natural point of Roman Barcelona, where a temple to Emperor Augustus once stood. A bronze plaque on the wall records the exact elevation. Travelers read the number to solve the puzzle, right outside the courtyard where the temple's columns still stand.

An eight-hundred-year-old house beside the Cathedral, home to a famous marble letterbox designed by architect Lluís Domènech i Montaner in 1895. Carved with swallows and ivy, it hides a small creature at the bottom of the design that travelers must identify to solve the step.

A quiet historic square behind the Cathedral, site of a tragic bombing during the Spanish Civil War in 1938. Memorial plaques explain the true history behind the marks still visible on the church facade. This is the final stop of the quest, where travelers complete their journey through the Gothic Quarter.