Ballet is so beautiful to watch but the training is insane!  
It really is. Modern ballet is a highly technical art form. Gosh, it even has its own vocabulary - based on French I believe.
I had forgotten the link with French.  Do you know the history of ballet in France?  I wonder when it became popular.
An aristocrat called Catherine de' Medici brought it from Italy to France in, I believe, the 15th/16th centuries.
I have read about the Medici family, especially Catherine, but had no idea there was a link with ballet.  Catherine was a formidable woman.
Catherine de' Medici's patronage of the arts
Catherine de' Medici's patronage of the arts made a significant contribution to the French Renaissance. Catherine was inspired by the example of her father-in-law, King Francis I of France (reigned 1515–1547), who had hosted the leading artists of Europe at his court. As a young woman, she witnessed at first hand the artistic flowering stimulated by his patronage. As governor and regent of France, Catherine set out to imitate Francis's politics of magnificence.
°) and half (180°) turns are possible for some types of turns
History.
Ballet is a type of performance dance that originated in the Italian Renaissance courts of the 15th century and later developed into a concert dance form in France and Russia. It has since become a widespread, highly technical form of dance with its own vocabulary based on French terminology. It has been globally influential and has defined the foundational techniques used in many other dance genres. Becoming a ballet dancer requires years of training. Ballet