Hundreds of thousands of people will head to Washington D.C. this week to celebrate the Fourth of July holiday. While they look up to enjoy the fireworks, there’s something else up there that’s a bit harder to see: rooftop farms. Kristof Grina, the co-founder and farm manager at Up Top Acres, says his goal is to restore nature in cities, and they do this by establishing gardens on top of commercial buildings. He says there’s a lot of rooftop space in the city that could be put to use. On the six acres of rooftop he manages, you'll find everything from raspberries and figs to carrots and cucumbers. Some roofs are home to honeybee hives and pollinator habitats for wild monarchs. It's not cheap to start farming on a roof, but commercial building managers are seeing a return on investment.