A leading U.S. newspaper and a venture capital firm ranked the top 10 cities for start-ups, based on dollars invested in young tech companies in 2011.

It should come as no surprise that San Francisco topped the list, but what about Chicago, Austin and Boulder? These areas make the list thanks to affordable real estate and strong talent pools. Boston, New York, L.A., Washington, D.C., San Diego and Seattle round out the list.

Watch this video highlighting why cities like Boulder and Denver are start-up magnets.