Ontario Lacus is the largest lake in Titan's southern hemisphere. This view of it was captured by the RADAR instrument on January 12, 2010. In the center left of the lake there is a visible dark channel running in to what seems to be a delta. The lake does not appear totally black because the radio waves actually penetrate through the liquid to the lake's bottom. To Cassini's cameras, the lake surface appears smooth and dark.

NASA / JPL