The Marius Hills are a set of volcanic domes located in Oceanus Procellarum on Earth's Moon. The domes are thought to have formed from lavas more viscous than those that formed lunar mares. These domes average approximately 200–500 m (660–1,640 ft) in height.[1][2][3] The Marius Hills take their name from the nearby 41 km (25 mi) diameter crater Marius.[4] These hills represent the highest concentration of volcanic features on the Moon.[5]