Portland, Ore, Courtesy of Forbes.com

Downtown Portland, Ore. offers food truck eats, independent theaters and a world-famous used bookstore.

When it comes to cities, Portland, Ore., is a unique urban playground of high-end culture, green living and DIY arts scenes. But for a taste of Portland's best, natives point to the city's downtown area. There you'll find independent live theater, beautiful parks, the largest independent, used bookstore in the country and some of the best doughnut shops on the Pacific Coast (not to mention a plethora of Portland's celebrated food trucks).

We located the country's most alluring downtowns with the help of travel experts from Frommer's and Livability, a travel and analysis site that focuses on mid-sized or smaller towns. While Livability's own list of best downtowns helped us narrow the playing field, we ultimately considered a wide variety of factors including attractiveness, accessibility, diversity of offerings, shops, restaurants, proximity of parks and cultural options.

Read more on Forbes.com:
In pictures: America's Best Downtowns
America's Most Dangerous Cities
The World's Tiniest Hotel Rooms
America's Best Chain Restaurants

Santa Monica, Calif., Courtesy of Forbes.com

A beautiful setting is just one reason why Santa Monica's downtown is a destination.

"We embraced the subjectivity that is inherent in a list like this, while still striving for benchmarks and criteria that we think make a great downtown," said John Hood, a Livability spokesman. Among those criteria they considered: entertainment options, navigability, attractive architecture and a thriving downtown.

Some cities, like Santa Monica, Calif., made the list because they both offer a lively downtown and have the luck of being in a beautiful setting. Located on one of the most enviable stretches of the California coastline, Santa Monica has a strong concentration of high-end shops and inventive restaurants that help lure residents and visitors away from shore. But it's not just the rich and famous that can enjoy Santa Monica's downtown -- there are enough single-family homes and apartments spread out through the area to ensure that a lively mix of people can live and work near the downtown area. "All of Santa Monica is pretty walkable and compact," says Jason Clampet, senior online editor for Frommers.com. "And it has some of the best views in the Los Angeles area of the ocean."