Planum Boreum (Mars)

This feature is named after an earlier feature.

Planum Boreum is the northern polar plain on Mars. It extends northward from roughly 80°N and is centered. Surrounding the high polar plain is a flat and featureless lowland plain called Vastitas Borealis which extends for approximately 1500 kilometres southwards, dominating the northern hemisphere. (wikipedia entry)

A planum is a plateau or high plain. On Mars they are named after the nearest named albedo feature on the Schiaparelli or Antoniadi maps.