The Cassini spacecraft has been orbiting Saturn since 2004, with frequent flybys of the largest moon Titan. With its thick atmosphere rich in nitrogen and hydrocarbons, it was once thought that Titan was covered in a global ocean of methane. Cassini optical and microwave imaging instruments have since revealed a world with a solid surface, strikingly similar in physical appearance to Earth, complete with lakes of liquid methane/ethane in the polar regions. Cassini RADAR altimetry data collected on the 49th flyby of Titan (2008 December 21) over Ontario Lacus, the largest lake in the south polar region, show signatures of a specular reflection so strong that it saturated the radar receiver. From the specular echo strength, which declines exponentially with increasing surface height variance, we are able to constrain the rms surface height variation to be less than 3 mm over the 100m-wide Fresnel zone. Lauren Wye will review her analysis of this data and the implications for wind speeds and surface material properties.