All 'high, flat pieces of land' in Antarctica are covered with ice. One notable flat area of ice is called the polar plateau.
You may be thinking of the polar plateau.
A stairway with a landing in the middle, I call a platform. In the USA, the flat, square area that separates a section of stairs is called a "landing". However, if the flat area is at the bottom of stairs outside, it may be a small (or large) patio.
Antarctica is not known for any 'flat land'. This is because 98% of the continent is covered with an ice sheet. You may be thinking, however, of the polar plateau, which is flat ice around the South Pole. This flat area offers the longest sight-line to the horizon on Earth, about eight miles.
A flat area is called a plane. A flat area the is elevated higher than all the surrounding land is called a plateau.
the high flat land is called " plateau".
It is called the surface area.
A large, flat area of land is called a plain.
mesa
the transom
praries
Area.
An area of flat land with higher surrounding land is called a valley.
a broad area of flat or gently rolling land is called a plain.