It's quickly clear that the squat gray building at 506-508 Natoma Street isn't any old property. The otherwise drab exterior is accented by a bright yellow door and a bright yellow…ball of yarn? Okay, it isn't literally a ball of yarn, but it's some sort of artistic orb that resembles a kitten's playtoy. Inside, a two bed-room artist's loft and a more reserved studio apartment take up a little more than 2,000 square feet of space. The lofts are up for sale as a pair asking $1.5 million.