The outer most wall, the one that was first destroyed by the titans is known as Wall Maria. Then the second wall is known as Wall Rose and the inner wall is called Wall Sheena, all three of them are 50 meters tall.
The Walls are named after the three daughters of Ymir Fritz, the king at the time when the walls were made.
Maria is the outermost wall, Rose is the second, separating the poor from the upper class, and Sina (pronounced and sometimes misspelled as Sheena) is the innermost wall, separating the upper class from the elite, and the royal family. They are named after King Fritz’s three daughters.