The Government yesterday announced that its banks would be closed until July 7, the country's stockmarket was suspended and cash machine withdrawals across Greece would be capped at €60 daily.
Riot police were on standby in Athens amid fears the Greek public may react violently to the unprecedented situation.
"I heard that the banks were going to shut this week so I came to take out some money," said Evi Costas, 40, just after her bank card was swallowed by a Eurobank ATM just off Syntagma Square.
"I wanted to withdraw €500, but what will I do now?"
With nearly half a billion euros removed from the banks on Sunday alone, the Government needed to keep the banks shut to stop them being emptied.
While the European Central Bank had strongly advised shutting the banks, Yanis Varoufakis, Greece's firebrand finance minister, had argued - before yesterday's move - it would mean admitting Greece's eurozone days were over.
Hence the continuation of the long lines of people outside the few ATMs that still had cash in them.
True, many of those queuing were simply anxious about having cash in hand for the next few days, rather than trying to remove their entire life savings and stash them at home.
But with confidence in Greek financial institutions at a historic low, the "Bank Under the Bed" is about the only one doing well at the moment.
Since Alexis Tsipras' Government was elected on its radical, anti-austerity ticket in January, anxious Greeks have withdrawn an estimated €30 billion from savings accounts, adding to a general sense of a 1930s-style meltdown.
"If we default and go back to using the drachma it will be like going back to the wartime era," added Costas.
"Only this time round, the drachma will be like some useless Third World currency with no value."
The fear Greece might eventually bow out of the euro has been around in Athens for months, but on Saturday what had once just seemed like a worst-case scenario suddenly loomed as the most likely outcome.
That was when Tsipras, having argued to the wire with eurozone leaders over the terms of the continued bailout programme - which is also due to expire tonight - suddenly announced he would put the matter to a national referendum this coming Sunday.
For a country that was the birthplace of democracy, that might sound like a reasonable plan.
It did not go down well, though, with eurozone finance chiefs, who saw it as yet more brinksmanship by Tsipras in his bid to make them blink first.
Yet in playing this latest hand of Greek financial poker, Tsipras also seems to have forgotten that the bank always has the upper hand.
For in postponing the decision on the bailout programme until next Sunday, he gambled that Brussels would extend the deal itself for a week, allowing it to make its €1.5 billion payment due to the IMF.
It was at that point that the eurozone's finance ministers shook their heads, saying that as Athens had "unilaterally" ended the talks, there would be no extension, not even for a few days.
While the ECB later said it would continue to throw Athens a financial lifeline, allowing local banks to continue withdrawing, the only thing both sides now agree on is that nobody really knows what will happen next.
Those waiting at the ATMs pass the time debating how they will vote in the referendum - not that it offers much of a choice either way.
Even those who favour leaving the eurozone seem to fear that Greece may end up, at the very least, like neighbouring Albania.
"Europe is a club of cannibals that is trying to strangle Greece," said Lambros Stamoulis, 29, one of the 25 per cent of Greeks unemployed.
"I will vote 'No' to the bailout in the referendum. It would be nice to stay in the euro, but the debt is so huge it would be best to return to the drachma."
"I will vote 'Yes'," said pensioner Costas Papadopolous, 75, after failing to withdraw his monthly pension at the National Bank of Greece ATM in Syntagma Square.
"Tsipras has been far too confrontational and he needs to go. In fact, if Europe stops giving us money, that might be a good idea, it might mean we get new elections."
With that he sauntered off, joining two friends who were whiling the hot afternoon away in a cafe. With the future now so uncertain, that seems about as much of a plan as anyone can make.
