Vienna experienced the 1873 stock-market crash known as Black Friday.
The Vienna Stock Exchange collapsed on May 9, 1873, after speculative investment had driven share prices sharply higher. The crash occurred during the Vienna World's Fair, an international exhibition that had helped create an atmosphere of optimism and commercial confidence. When several banks and companies failed, panic spread through the exchange.
The shock helped trigger the Panic of 1873, an international financial crisis. Problems soon appeared in other markets, including Germany and the United States. Railways, banks, and construction companies were especially exposed because the preceding boom had relied heavily on credit and ambitious investment.
This Black Friday should not be confused with the later retail phrase or with the British Black Friday of 1866. In the 1873 context, it specifically refers to the Vienna exchange collapse and its role in a wider crisis sometimes called the Long Depression.