The official name of the region on Mars known as the Tharsis Ridge or Tharsis Bulge, a large raised area in the northern hemisphere of Mars, centered at 2.8 °N, 113.3 °W. It takes its name from the ancient Spanish town known formerly as Tartessus. Tharsis is a large uplifted area, measuring 2105 km across at its greatest dimension, which contains the planet's most prominent volcanoes