The first coin with a hologram in the history of Polish numismatics! In 2001, the National Bank of Poland launched a series of "Polish Ritual Year", which aims at presenting the unique and most beautiful customs and traditions of Polish culture. So far it has been published: in 2006: Kupala Night in 2004: Dożynki in 2003: Śmigus-Dyngus in 2001: Carol Singers On the reverse of the coin, in the central part, the hologram presents a stylized image of a fern flower, changing colors depending on the angle of view - this is the most famous symbol of Midsummer Night.  Kupala Night (also known as Sobótka) falls on the shortest night of the year, that is, from June 23 to 24. The ritual of Kupala Night still derives from pagan tradition.  It was believed that a fern at midnight blossoms for a moment, and its big and beautiful, shining at night flower has an extraordinary power. At dawn, boys and girls would return to the still burning bonfires to jump through the flames after grazing with a mugwort, holding hands. This custom ended the ritual of passing through water and fire, probably constituting a ritual of marriage. The legends of the fern flower, also known as the "Perun Flower", are known from various legends and have survived to this day in many countries. It is also worth mentioning the unique nowadays phenomenon, which is the annual official celebration of Sobótka in many cities in Poland.