Hecates Tholus
Hecates Tholus is a Martian volcano, notable for results from the European Space Agency's Mars Express mission which indicate a major eruption took place 350 million years ago.
The volcano is at location 32.1°N 150.2°E, in Elysium Planitia, and has a diameter of 183.0 km; the eruption created a caldera and two depressions apparently full of glacial deposits, including ice. It is the northernmost of the Elysium volcanoes; the others are Elysium Mons and Albor Tholus.
In planetary nomenclature, a "tholus" is a "small domical mountain or hill".