To keep credit available, it let financial institutions borrow money at rock-bottom rates for longer periods than before. Where once commercial banks earned interest on money they deposited at the central bank, the Governing Council began charging them a penalty, a so-called negative interest rate. The aim was to force skittish banks to lend.

The measures culminated in early 2015, when the European Central Bank began using newly created money to buy bonds and other assets, a program that has cumulatively been worth more than €2 trillion, a sum roughly equal to the annual economic output of India.

As that tide of cash recedes, the hazards below the surface will come into view.

The list is long. For one, Italian banks are still laden with bad loans. Italy’s public debt is so high that the country spends 4 percent of its gross domestic product just paying interest.

Elsewhere, real estate prices in German cities like Frankfurt have risen so much that there is fear of a property bubble. Stock prices are at record-high levels and may be overdue for a correction. And Britain’s impending exit from the European Union will disrupt the economic order.

Consumers, businesses and politicians have also gotten accustomed to — or spoiled by — low interest rates. Investors are so desperate for safe places to put their money that corporations like Daimler, the German automotive giant, have been able to issue bonds that pay no interest.

Low rates have also weakened the euro against other currencies, a boon for exporters whose products are usually cheaper for foreign customers as a result. The euro will most likely rise as monetary policy returns to normal, making it harder for some businesses to compete.

For now, the eurozone economy is humming. But that may be no insurance against another crisis. Such events have occurred regularly since the world’s economic powers abandoned fixed exchange rates in 1973, a recent report by analysts at Deutsche Bank pointed out. They listed the withdrawal of central bank support as one factor that could trigger the next meltdown.