Placa del Rei

If Barcelona has a single spot where you can feel the weight of medieval power, it's this enclosed square tucked deep in the Gothic Quarter. The Placa del Rei was the courtyard of the Palau Reial Major — the royal palace of the Counts of Barcelona and Kings of Aragon from the ninth to the fifteenth century. Stand in the center and you're surrounded on three sides by walls that have witnessed coronations, inquisitions, and one of the most famous audiences in history.

The Salo del Tinell, the palace's great hall, is a stunning feat of fourteenth-century engineering: six massive stone arches spanning seventeen metres without a single column for support. It was here, according to deeply ingrained local legend, that King Ferdinand and Queen Isabella received Christopher Columbus in 1493 after his first voyage to the Americas. Whether or not the meeting actually happened in this room is debated by historians, but the story is too good for Barcelona to let go.

Beneath the square lies one of the city's best-kept secrets: an underground archaeological site run by MUHBA, the Barcelona History Museum. Descend below street level and you can walk through the excavated streets, shops, wine-making facilities, and fish-sauce factories of Roman Barcino, dating from the first century BC to the sixth century AD. The preserved area covers about 4,000 square metres — one of the largest underground Roman sites in Europe.

Above ground, King Martin's Watchtower rises five stories from the corner of the square. Built in the fifteenth century as a lookout, it offers views across the rooftops of the old city. Next to it stands the Royal Chapel of Saint Agatha, a fourteenth-century chapel with a distinctive crown-shaped octagonal bell tower.