5 Big Ideas To Make Cities BetterBarcelona thinks it can create a city-wide "trust network" to take care of elderly residents.Lisbon wants to turn kinetic energy from commuters into electricity for the city. Schaerbeek, acity in Belgium, hopes to use 3-D geothermal mapping to help residents conserve energy.These ideas are just a handful of the proposals from the 21 European cities selected asfinalists in the Bloomberg Philanthropies latest Mayors Challenge.

In 2012, Bloomberg Philanthropies announced the first iteration of the Mayors Challenge: Acall for U.S. cities with at least 30,000 residents to come up with innovative ideas addressingsocial issues, government accountability, economic problems, customer service, and more.Ultimately, Providence, Rhode Island beat out 20 finalists with Providence Talks, an earlyeducation initiative for kids in low-income households. Providence took home $5 million forits efforts.

This time around, Bloomberg Philanthropies challenged European cities with at least100,000 residents to enter the competition, which has a grand prize of €5 million and fourrunner-up prizes of €1 million each. Below, check out some of our favorite finalists:

Schaerbeek, Belgium's plan to use flyover and 3-D geothermal mapping technology togenerate "personalized energy guides" for each home in in the city, and to offer anincentive system to motivate citizens to take action. The reasoning: Lots of people inSchaerbeek are dealing with high energy prices, but few are making energy-savingupgrades.Warsaw, Poland's Urban Information System for Visually Impaired--a proposal to makelife easier for the blind and visually impaired by scattering thousands of beacons aroundthe city. The beacons communicate with visually impaired users via mobile apps,helping them find their way.Lisbon, Portugal's plan to save energy by capturing kinetic energy from commuters andturning it into electricity.An initiative from Kirklees, U.K., to deal with government budget cuts by leveragingunused local resources--everything from trucks to lawnmowers to human skills--andmaking them available for trading, borrowing, and time-banking on an online sharingplatform.Bologna, Italy's proposal to address rampant youth unemployment by launching

entrepreneurship training and skills-building initiatives in schools and youth centers,and by opening pop-up education labs to teach coding and related skills.

James Anderson, head of government innovation programs at Bloomberg Philanthropies,says that there are some distinctive patterns and themes in this year's batch of finalists. "[Thefinalists] are less about government going it alone and more about government movingtogether with citizens and civil society," he says. "There's also a huge emphasis on making bigdata personal and showing the value of these technological advances in the lives of individualcitizens."

In Krakow, Poland, for example, the city is proposing a unified transit incentive program thatwill offer personalized incentives to citizens. And in London, the local government wants toleverage sensors, apps, and websites to help citizens track their health and assist the city infinding at-risk patients.

Major themes among the applicants include youth unemployment, energy efficiency (therewas a bigger focus on this in the European entries than in the U.S. entries), obesity, economicgrowth, and social inclusion and aging.

The winner and runners-up of the competition won't be announced until the fall. In June, allthe finalists go to Ideas Camp--a two-day bootcamp in Berlin where cities are expected tostrengthen their ideas. They continue to work with individual coaches until the end of July,when they re-submit their ideas for judging.

Bloomberg Philanthropies hasn't yet decided whether it will launch another MayorsChallenge when this one ends. "We’re optimistic, but we haven’t made any plans," saysAnderson.