Ceraunius Tholus is a volcano on Mars located in the Tharsis quadrangle at 24.25° north latitude and 262.75° east longitude, part of the Uranius group of volcanoes. Earlier interpretations suggested that it is a stratovolcano. The slopes on Ceraunius Tholus are quite steep with an average slope of 8° with many radial erosion channels and pitted valleys extending from just below the rim of the caldera toward the base of the volcano. (wikipedia entry)
A tholus is a small domical mountain or hill. On Mars they are named after the nearest named albedo feature on the Schiaparelli or Antoniadi maps.