This mosaic of image swaths from Cassini's Titan Radar Mapper, taken with the synthetic-aperture radar (SAR), features a large dark region several hundred kilometres across that differs in several significant ways from other potential lakes observed on Titan. It is not as dark to the radar as many lakes (including the lakes seen here), and the nature of the margin is unusual. It has many characteristics in common with lakes, including its channels and interior, yet its differences distinguish it from other similar features.