This type of hat is called phareon and is a garrison cap with a long gold tassel.
It is part of the uniform that “Evzones”, an elite light infantry unit of the Greek army, wears. Evzones are the members of the Greek Presidential Guard, an elite ceremonial unit that guards the Greek Tomb of the Unknown Soldier, in front of the Greek Parliament.
(Please note all sizes are in European measure (centimeters). For more information around size conversion please visit the FAQ page.)