If you’re looking for the latest innovations in sustainability, Denver is the place to be on July 27, as the city is hosting a 36-hour civic hackathon.

Presented by PlaceMatters and the Partnership for Sustainable Communities, the event will bring together programmers, government agencies and nonprofit organizations to “build and improve the latest apps that bring sustainability into the forefront of everyone’s lives,” according to the event website. The hackathon is free to enter.

Examples of the kinds of applications that might be built include programs that focus on regional transportation, housing and finances.

At the end of the event, the top three apps will be chosen with a chance of receiving support from government partners to finish the projects.

Hackathons are continuing to rise in popularity among cities. San Diego held a 24-hour hackathon in March searching for the next “great city app,” while San Francisco hosted its own hackathon last year to search for ways to improve transparency.