To illustrate how strange this may seem today, one can imagine churches and cathedrals having, just like banks, large underground safes and people going to church to pray and... withdraw money.
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Because temples were occupied by priests and devout workers and because they were usually heavily guarded, they were considered as depositories of unquestionned security. Wealthy Romans commonly stored their money in various temples at various locations so that they could gain easy access to it without the burden of carrying it around. Having their money in various temples also decreased the risk of loosing their entire fortune in case a temple caught fire or was attacked. There were literally thousands of temples throughout the Roman territories that were also repositories. The Temple of Saturn in Rome, still visible today, housed the Aerarium or Rome's public treasury. The Temple of Castor and Pollux became the depository for the State treasury during the imperial period. Some temples, such as the Juno Moneta temple, also minted money.
It is only during the Empire, that public deposits were in majority held in private repositories rather than in temples.
They were however other types of bankers in ancient Rome. The argentarii were money changers and their role became more important as commerce and trade expanded throughout the Mediterranean between the 3rd century BC to the 3rd century AD. The image of Jesus overthrowing the tables of the money changers in the temple in Jerusalem comes to mind. Money changers had shops and stalls in the Forum, not far from the large temples. The first money changers were actually called trapezites (from the Greek word trapeza which means counter). They were Greek bankers dealing with bank transactions in counting houses around the Forum, for example exchanging drachmas for sesterces or vice versa. Because Greek commerce in the Mediterranean was dominant at the beginning of the Roman Republic, they were the first bankers in Rome. The Greek term was overtime replaced by the Latin term argentarii (also called argenteae mensae exercitores, argenti distractores or negotiatores stipis argentariae) or the Roman money changers.
The argentarii were private and free individuals totally independent from the State who belonged to a guild which accepted only a limited number of new members. Their shops or stalls around the Forum were state-owned property and built by the censors. Their main function was to exchange foreign currency for Roman currency (permutatio in Latin). Their functions expanded over time to include almost every money transaction including holding other people's money, lending money, participating in auctions, determining the value of coins and detecting forged coins, and circulating newly minted money. The argentarii’s reputation could vary. Some were highly respected and belonged to the upper class, usually the ones carrying business on a large scale and with very wealthy clients. Some were looked down upon, usually the ones charging usury rates and doing business on a small scale and/or involved in shady transactions.
During periods of general poverty which were often the periods when Rome was at war, the problem of citizens' indebtedness was important and represented a threat to the stability of the Republic. In ancient Rome, being unable to fulfill one's debt obligations did not mean a bad credit file. It potentially meant slavery for the average citizen!
To solve the problem of people's indebtedness, public bankers called the mensarii were introduced in 352 BC. A five man commission called the quinqueviri mensarii was created along with a public bank. The quinqueviri mensarii would cover from public resources citizens who could provide enough security (for example, a property). Citizens who could not provide enough security, gave up their property to their creditors after proper valuation of their property by public officials. Over a century later, in 216 BC, a commission of three people was created with wider functions.
Mensarii were often confused with the argentarii even in ancient times even though they were public, not private, bankers. Over time the functions of the mensarii became very similar to that of the argentarii: they held deposits, they determined the value of coins, tested the genuineness of money, etc. The mensarii had an excellent reputation and were highly respected. Their role was considered positive as they were able to address the problem of excess debt and solve many people's debt problems.
They were sometimes called upon when large transactions were involved in order to test the genuineness and value of coins, just like the argentarii. Actually many of the nummularii's functions were the same as the argentarii's: they exchanged foreign currency for Roman currency, they held deposits and lent money, they participated in auctions and large commercial transactions, they made payment of behalf of clients and executed payments abroad through local bankers.
Ancient Roman banking was quite sophisticated and banking activities were quite similar to modern-day banking, be they the widespread use of credit, foreign exchange, the use of cheques or the detailed recording of transactions. The sophistication of banking activities is also a reflection of the incredible advancement of Roman society.
The argentarii's functions