Mackay Lacus (Titan)

Lake in Australia.

Mackay Lacus is the seventh largest of a number of hydrocarbon seas and lakes found on Saturn's largest moon, Titan. The lake is composed of liquid methane and ethane, and was detected by the Cassini space probe. (wikipedia entry)

A lacus is a "lake" or small, dark plain with discrete, sharp boundaries. On Titan they are named after lakes on Earth, preferably with a shape similar to the lacus or lacuna on Titan.