There are many reasons a city could be home to a large number of very wealthy people. The place could be a great economic and financial center, or it could be so beautiful or culturally significant that people to whom money is no object are especially attracted to it. And a friendly tax code certainly doesn’t do any harm either! And a lot of the times, it’s a combination of two or more of these reasons.

As an indication of how “wealthy” a city is, we’ve taken into account the “millionaire density”, or the percentage of its inhabitants who are millionaires (as determined by WealthInsight). According to this metric, the world’s top 10 richest cities are:

10. Florence, Italy – 2.59% Millionaires

Kicking off the list is the charming Italian city of Florence – which is kind of surprising. The place is mostly known for its stunning Renaissance architecture and is frequently ranked among the most beautiful cities in the world. This is perhaps what draws very wealthy people there, as Florence isn’t a particularly important industrial and financial center. Almost 2.6% of people living within its limits are millionaires.

9. Amsterdam, the Netherlands – 2.63% Millionaires

Charming and picturesque Amsterdam, the capital and largest city of the Netherland, might not look like a global metropolis, but it was once at the center of a huge commercial empire controlled by the mighty Dutch navy. So it’s no surprise that it is the home of the world’s oldest stock exchange, but also lots of big modern corporations like Phillips, Heineken International or, ING Group. About 2.6% of the people who inhabit the city are millionaires.

8. Singapore – 2.80% Millionaires

Perhaps the first entry on this list that isn’t at all surprising, Singapore boasts one of the region’s leading economies and is considered one of the Four Asian Tigers (alongside Hong Kong, Taiwan, and South Korea). In addition to the many millionaires and billionaires who have made their fortune locally and in other Asian countries, Singapore’s friendly tax rates have also attracted some of the West’s super-rich, most notably Facebook co-founder Eduardo Saverin. Out of the city-state’s total population, 2.8% are millionaires.

7. Oslo, Norway – 2.90% Millionaires

Norway is one of the most stable, best run countries in the world, and also benefits from having an abundance of natural resources, so it’s not much of a surprise to hear many people living in the country are very well off. The city is the country’s economic and governmental center, and can often be found at the top end of surveys and studies of the world’s most expensive cities to live in. These expenses shouldn’t be a problem for the 2.9% of Oslo’s population who are millionaires.

6. London, the United Kingdom – 3.39% Millionaires

London is without a doubt one of the world’s great cities. A prominent cultural and political center, as well as a very important financial hub, it was once the capital of one the greatest empires the world has ever seen. Even today, signs of its glorious past can be seen everywhere, alongside modern edifices showcasing its current importance and wealth. Almost 3.4% of its inhabitants are millionaires.

5. Frankfurt, Germany – 3.88% Millionaires

Frankfurt lies at the heart of German financial and economic system, and given Germany’s huge economy (the largest in the EU), this makes it one of the most important cities in all of Europe. It is home to Germany’s largest stock exchange, as well as the country’s most prominent banks, an extremely busy international airport, and even the European Central Bank. Unsurprisingly, Frankfurt is also the most expensive city in Germany, as well as being the richest, with about 3.9% of the people living there being millionaires.

4. New York City, the United States – 4.63% Millionaires

Among all the cities on the planet, New York is perhaps the most worthy to be called the capital of the world. It’s is a great cultural center and an extremely important financial hub (two words: Wall Street), home to some of the most iconic landmarks and some of the best universities in the world, as well as holding a prominent place in the entertainment industry. All of this attracts a lot of visitors, a whopping 55 million a year, but also some of the world’s wealthiest people, many of whom live in its lavish sky-scrapers. Out of the entire population, around 4.6% are millionaires.

3. Geneva, Switzerland – 17.92% Millionaires

The second most populous Swiss city is also the country’s second richest. Geneva is the biggest French-speaking city in Switzerland and a very important place in both the world of science and diplomacy. CERN and the Large Hadron Collider are based in Geneva, and so are many international organizations, like the Red Cross or the World Trade Organization (WTO). It’s also the home of the United Nations` European headquarters and even has one of the world’s most expensive streets

Also, the Swiss have a reputation as great bankers, and Geneva is not an exception to that rule. All of this attracts some very affluent people to the shores of Lake Geneva, to such an extent that almost 18% of the people there are millionaires.

2. Zurich, Switzerland – 27.34% Millionaires

In many ways, Zurich is Geneva’s German-speaking counterpart. It is the largest and richest city in Switzerland and although not as prominent on the international political scene, it is just as influential in the world of finances and banking. The Swiss Stock Exchange is located here, alongside some of the country’s leading financial services companies, like UBS and Credit Suisse. It is also home to the Swiss Federal Institute of Technology (ETH Zurich), widely regarded as one of the best universities in Europe and one of the best in the world in the areas of science and engineering (you might recognize a certain Albert Einstein, who was a student there a century ago).

More than a quarter of the city’s inhabitants are millionaires.

1. Monaco – 29.21% Millionaires

Monaco is a city basically created by and for the super-city. A hundred and fifty or so years ago, this was the last place you’d expect would attract the world’s wealthy and famous, but its great location and climate, as well as the gambling facilities, eventually made the city-state extremely popular. And it’s very low tax rates certainly help as well! Nowadays, its multiple marinas and luxurious properties accommodate many of the world’s wealthiest people and their yachts. Amazingly, one in three of Monaco’s residents is a millionaire.