In 1137, Barcelona’s count Ramon Berenguer IV married Petronilla of Aragon, uniting Catalonia with the Kingdom of Aragon into the Crown of Aragon. Over the next centuries, Barcelona became a maritime and commercial powerhouse with colonies and influence across the Mediterranean, from Sicily to Athens. The city flourished culturally and economically but also faced challenges like the Black Death and internal conflicts. Still, this period saw the rise of Catalan language, law, and institutions—many of which survived well into the modern era.