The Sokol movement (from the Slavic word for falcon) was a youth sport movement and gymnastics organisation founded in 1862 by Miroslav Tyrš and Jindřich Fügner. The Sokol played an important part in the development of Czech nationalism through the organisation of gymnastic festivals called Slets.
This poster advertises a celebration planned to coincide with the sporting events, a pageant which would take place on an island on the river Vltava with spectators seated on both sides.
As it happened, the event nearly ended in tragedy. Barges filled with singing actors were struck by a strong gust of wind on their way to the island. They were separated from the boat towing them and were carried down the river by the wind towards a weir. Panic ensued and it was only by good fortune that no one was drowned.