On the 15th of August every year the Feast of the Assumption of the Blessed Virgin Mary (or The Dormition of the Theotokos) is celebrated throughout Greece. It is an observed national holiday that commemorates the death (the "falling asleep" as we call it) of the Mother of Christ and her bodily assumption into Heaven. Because it signifies the Blessed Virgin's passing into eternal life, it is the most important of all the holidays pertaining to the Virgin Mary.
In all of Greece there are events and celebrations held on this day with rich traditions which vary from place to place. Churches are filled and many take the Holy Communion to break their previous 14-day fasting.
Families gather to celebrate in the typical Greek way which means tons of food and sweets and music, of course. The party escalates if you happen to be named Mary, Maria, Marie, Panagiota, Panagiotis, Despina, or any other name derived from the Virgin Mary because then it is your Name Day.
The feast day happens to coincide with the period of time that most Greeks go on their summer vacations. There is a great, frenzied exodus from the cities, especially Athens, as people depart and head to their hometowns -- villages and island homes. All over Greece, rooms are hard to find, tickets on ferries are almost impossible to get and tourist places become very crowded. (So plan your trip to Greece wisely and very early!)