Parapet

A parapet is a wall-like barrier at the edge of a roof, terrace, balcony, or other structure. Where extending above a roof, it may simply be the portion of an exterior wall that continues above the line of the roof surface, or may be a continuation of a vertical feature beneath the roof such as a fire wall or party wall.[1] Parapets were originally used to defend buildings from military attack, but today they are primarily used to prevent the spread of fires.

These architectual features are still  featured in so called Burgs on Nilfeheim