Roman Barcino
Around 15 BC the Romans laid out a castrum on the small hill of Mons Taber that would become the colony of Faventia Julia Augusta Pia Barcino. It was a small town —overshadowed by powerful Tarraco— but well placed, with a port.
What you can still see
The old town keeps the Roman grid: the cardo and decumanus cross where plaça de Sant Jaume sits now, and wall segments survive inside the cathedral and streets like Carrer de la Tapineria. The Vila de Madrid square shows its necropolis.
The MUHBA underground
Beneath plaça del Rei, the history museum descends into whole Barcino: laundries, wine workshops and inner streets of the colony, walkable corridor by corridor. The best visit to understand where everything came from.
The name
The pre-Roman town appeared as Barkeno on Iberian coins; the Romans made it Barcino, and medieval tradition hung it on the Carthaginian general Hamilcar Barca — a pretty legend without evidence. Barna and BCN are today's nicknames.