Systems and methods for visualizing ablated tissue are disclosed. In some embodiments, a system for imaging tissue comprising: a catheter having a distal end and a proximal end; an inflatable balloon disposed about the distal end of the catheter; and an optical housing extending from the distal end of the catheter into the balloon, the optical housing being configured to position inside the balloon a light source for illuminating a tissue outside the balloon and a camera for imaging the illuminated tissue.