The flag used is the Flag of Europe, which consists of a circle of 12 golden stars on a blue background. Originally designed in 1955 for the Council of Europe, the flag was adopted by the European Communities, the predecessors of the present Union, in 1986. The Council of Europe gave the flag a symbolic description in the following terms, though the official symbolic description adopted by the EU omits the reference to the “Western world”:
Against the blue sky of the Western world, the stars symbolise the peoples of Europe in a form of a circle, the sign of union. The number of stars is invariably twelve, the figure twelve being the symbol of perfection and entirety.
— Council of Europe. Paris, 7–9 December 1955.
United in Diversity was adopted as the motto of the Union in the year 2000, having been selected from proposals submitted by school pupils. Since 1985, the flag day of the Union has been Europe Day, on 9 May (the date of the 1950 Schuman declaration). The anthem of the Union is an instrumental version of the prelude to the Ode to Joy, the 4th movement of Ludwig van Beethoven’s ninth symphony. The anthem was adopted by European Community leaders in 1985 and has since been played on official occasions. Besides naming the continent, the Greek mythological figure of Europa has frequently been employed as a personification of Europe. Known from the myth in which Zeus seduces her in the guise of a white bull, Europa has also been referred to in relation to the present Union. Statues of Europa and the bull decorate several of the Union’s institutions and a portrait of her is seen on the 2013 series of Euro banknotes. The bull is, for its part, depicted on all residence permit cards.
Charles the Great, also known as Charlemagne (Latin: Carolus Magnus) and later recognised as Pater Europae (“Father of Europe”), has a symbolic relevance to Europe. The Commission has named one of its central buildings in Brussels after Charlemagne and the city of Aachen has since 1949 awarded the Charlemagne Prize to champions of European unification. Since 2008, the organisers of this prize, in conjunction with the European Parliament, have awarded the Charlemagne Youth Prize in recognition of similar efforts by young people.
Source: Wikipedia, https://en.wikipedia.org/wiki/European_Union#Symbols (10.01.2020)