What is a Vienna roll?

The Kaiser roll, also called a Vienna roll or a hard roll (original name: Semmel or Kaisersemmel; if made by hand also: Handsemmel), is a kind of bread roll, supposedly invented in Vienna, and thought to have been named to honor Emperor Franz Joseph. It is a typically crusty round roll made from flour,barm, malt, water and salt, with the top side usually divided in a rotationally symmetric pattern of five segments, separated by curved superficial cuts radiating from the centre outwards. Kaiser rolls are often produced by machine, as well as by hand.

from Wikipedia