If you live near a metropolitan area and are in need of business advice or are seeking networking opportunities, it's likely that you know right where to go. Perhaps it's a local accelerator, a meetup group, or a university seminar.

But you can probably also remember a time when these open collaboration and innovation opportunities weren't always so easy to come by. They're on the rise now thanks to the ongoing development of innovation districts, according to a new report from the Washington, D.C.-based Brookings Institution, a nonprofit research organization.

"Innovation districts constitute the ultimate mash up of entrepreneurs and educational institutions, start-ups and schools, mixed-use development and medical innovations, bike-sharing and bankable investments--all connected by transit, powered by clean energy, wired for digital technology, and fueled by caffeine," wrote the report's authors Bruce Katz and Julie Wager.

The formation of these "innovation districts" isn't as random as you might think. Katz and Wager identified three different models that explain how these collaboration-friendly areas have come to be. From Seattle to North Carolina, here's a look at how open innovation communities are born.

1. Anchor Plus Model

Katz and Wagner define anchors as "research universities and research-oriented medical hospitals with extensive R&D." So "anchor plus" districts include at least one hub institution that inspires a rise of nearby related firms and startups.

Key characteristics:

Presence of anchor institution(s)

Found in city downtowns and mid-towns

Located in mixed-use developments

Prime example:

Kendall Square, Cambridge, Massachusetts

Kendall Square is anchored by the Massachusetts Institute of Technology. The area abounds with opportunities for collaboration, as Harvard University and Massachusetts General Hospital are right next door. MIT also has a history of fostering university/ industry partnerships.

In the 1950s it began allowing for the use of university-owned land as a breeding ground for these partnerships. That effort is partly responsible for the cluster of life sciences and pharmaceutical companies that now exist in the area. Kendall Square has also seen the opening of brand-new restaurants and retail outlets as well as nearly 1,000 new housing units since 2005.

2. Re-imagined Urban Areas Model

This kind of district is the result of a makeover to a once industrial or warehouse area. The change is enabled by the area's close proximity to downtown as well as access to transportation.

Key characteristics:

Availability of renovated buildings along city waterfronts

Located in high rent cities

Close to research institutions and anchor companies

Prime example:

South Lake Union, Seattle

Katz and Wagner call the transition of the South Lake Union (SLU) from a run-down warehouse district to a mixed-used development "one of the most dramatic urban transformations in the United States."

Vulcan Real Estate, which is owned by Microsoft cofounder Paul Allen, spearheaded the change by persuading the University of Washington to locate its medical and bioscience campus in SLU in the early 2000s. Health care and life science firms soon followed. Entrepreneurial business was added to the mix when Amazon decided to locate its global headquarters there in the late 2000s.

3. Urbanized Science Park Model

This model involves the reversing of an old trend where corporations moved out to the suburbs, isolated from other firms as well as retail shops and restaurants. The urbanized science park is seeing formerly sprawling areas become increasingly dense with businesses, housing and restaurants.

Key characteristics:

Located in a suburban or exurban area

Increasing urbanization

Prime example:

Research Triangle Park, North Carolina