Solis Lacus /ˈsɒlɪs ˈleɪkəs/ (26°S 85°W / 26°S 85°W), (Latin, "lake of the sun") is a dark feature on Mars. It was once called "Oculus" and is still commonly called "The Eye of Mars" because with the surrounding light area called Thaumasia it resembles the pupil of one. Solis Lacus is known for the variability of its appearance, changing its size and shape when dust storms occur.
Percival Lowell believed that it was the planetary capital of Mars due to the number of canals he claimed intersected at the region.