Ismenius Lacus is the name of a telescopic albedo feature located at 40° N and 30° E on Mars.
The term is Latin for Ismenian Lake, and refers to the Ismenian Spring near Thebes in Greece where Cadmus slew the guardian dragon.
Cadmus was the legendary founder of Thebes, and had come to the spring to fetch water.
The name was approved by the International Astronomical Union (IAU) in 1958.

There appeared to be a large canal in this region called Nilus.
 Since 1881–1882 it was split into other canals, some were called Nilosyrtis, Protonilus (first Nile),and Deuteronilus (second Nile).
Ismenius Lacus is the name of a telescopic albedo feature located at 40° N and 30° E on Mars. The term is Latin for Ismenian Lake, and refers to the Ismenian Spring near Thebes in Greece where Cadmus slew the guardian dragon. Cadmus was the legendary founder of Thebes, and had come to the spring to fetch water. The name was approved by the International Astronomical Union (IAU) in 1958.
There appeared to be a large canal in this region called Nilus.  Since 1881–1882 it was split into other canals, some were called Nilosyrtis, Protonilus (first Nile),and Deuteronilus (second Nile).
Ismenius Lacus quadrangle