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A vast plain extending across the northern lowlands of Mars, more than 3,500 km in diameter. To the south and west it is bordered by the Martian highlands of Syrtis Major Planum and Arabia Terra, forming a solid region of higher land broken by a broad circular 'bay' of Utopia Planitia known as Isidis Planitia. To the southeast the plain runs up against Elysium Planitia and its crop of volcanoes (notably Elysium Mons). Extending northward from Elysium is the long narrow range of the Phlegra Montes, which separates Utopia Planitia from Arcadia Planitia to the east.
The plain of Utopia Planitia forms the shape of rough circle, due to its origins in an ancient and cataclysmic impact event. From a distance, its surface appears almost flat and unbroken, apart from a handful of small craters. The largest of these craters is the 104-kilometre Mie in the eastern part of the basin, notable as lying near the site where the Viking 2 probe landed on Mars in 1976. To the west from Mie is the only other significant crater on the plain, Nier, which is 46 km in diameter.
In fact the plain of Utopia Planitia is not flat and featureless, but is wrinkled by numerous patterns of ridges and escarpments extending outward from the central regions of the impact basin. The Cydnus Rupes run northward towards the great northern plain of Vastitatas Borealis, while the Utopia Rupes run westward and the Hephaestus Rupes lead southward toward the hills of Nepenthes Mensae. At a closer scale, the surface of Utopia Planitia is densely strewn with numerous rocks and boulders, many distorted into strange forms by the regular biting windstorms that pass over the surface of Mars.
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