Heavily populated cities often lack in green space and recreational areas, so the folks at Danish firm JDS Architects took this matter into their own hands by creating this rooftop playground that spans the top of three penthouses in Copenhagen. The playground features a shock-absorbing surface that is perfect for hosting lots of ruckus without annoying the habitants below. And for the adults who just want to chill amidst the cityscape, this playground also boasts a viewing platform. Lucky kids. [My Modern Met]