Vastitas Borealis is the largest lowland region of Mars. It is in the northerly latitudes of the planet and encircles the northern polar region. Vastitas Borealis is often simply referred to as the northern plains or northern lowlands of Mars. The plains lie 4–5 km below the mean radius of the planet. To the north lies Planum Boreum. A small part of Vastitas Borealis lies in the Ismenius Lacus quadrangle.