Sorry I know this is very subjective, but I'll try to explain. I remember reading that Bohemia was one of the wealthiest areas of Europe before WWII, and even though nowadays we don't exactly think of the Czech Republic as depressed, it still doesn't cross most of our minds as having been on the same level as Southeast England or the Netherlands, for example. This got me wondering if any areas that are now not known for their wealth were ever seen as world leading, sort of how Al-Andalus was the center of civilization for some time during the Medieval period (at least people say this anyway).
So during and immediately after the American Civil War, cotton prices, worldwide, skyrocketed. One of the greatest beneficiaries of this, for a time, was Egypt, which was a huge cotton producer. Nowhere near US levels, (I once tried to compare relative production for an essay I did and it's hard to overstate just how much cotton the United States was producing) but still, a major player in the international market.
Flush with this cotton money they funded all sorts of different projects, the built a world class opera house, funded and built the Suez Canal, built railroads, telegraph lines, internal canal and irrigation systems. In 1867 they reformed into the "Khedivate" which also granted them even more independence from the Ottomans than they had enjoyed before. They brought in foreign architects and built modern downtown Cairo in glorious belle epoque style with large boulevards and huge squares, including Tahrir.
Unfortunately for Egypt American cotton production reached pre-war levels within about a decade and the price crashed. Egypt turned to international loans to finance their enormously expensive projects. The terms of the loans were extortionate, and when they defaulted the English and the French assumed administration of the country's finances, culminating in full British occupation in 1882.
The bubble didn't last long enough for them to have ever been "one of the wealthiest areas" of the world, but it was a very bright flash of brilliance.
Source: A lot of this is covered in The Middle East in the World Economy, 1800-1914 by Roger Owen. For the projects of the Khedivate and Egypt's Bankruptcy, PJ Vatikiotis's "Modern History of Egypt" is quite good.