Barcelona

On 4 April 801, Louis the Pious captured Barcelona after a seven-month winter siege. History would remember him as the weeping, penitent emperor who let the Carolingian Empire fall apart. On this morning he was twenty-two, and had just done something his father never managed.

On 20 January 1401, Barcelona's city council opened the Taula de canvi in the Llotja de Mar - a public bank that guaranteed deposits with tax revenue, cleared payments by ledger, and showed what happens when a state treats its own credit as infrastructure.