These days, it seems like start-up hubs are everywhere.

Silicon Valley and Silicon Alley capture a lot of attention, but cities including Detroit, Michigan; Las Vegas, Nevada and Omaha, Nebraska each boast booming entrepreneurial communities of their own. Heck, even Canada is in the running for next start-up frontier.

However, some off-the-Silicon-path communities are better for entrepreneurs than others, according to Brad Feld, Managing Director of the Foundry Group and author of Startup Communities: Building an Entrepreneurial Ecosystem in Your City.

Feld wrote about the importance of "entrepreneurial density"--or the ratio of start-up founders and those they employ to the general population of a city--in his book, and emphasized the belief that access to easy capital is what makes or breaks a start-up community on his blog.

Richard Florida, a senior editor at The Atlantic, latched onto Feld's idea of mapping capital-rich start-up centers in a series of articles published this month. Here are 20 of the most capital-dense start-up communities in the country, according to his research.

20 metro areas