Swiss National Day. The tradition to celebrate the National Day on August 1st began in 1891.
A radio broadcast by the President of the Swiss Confederation is usually listened to by many Swiss. Communal celebrations are the fun part and usually include some sort of cultural life. Sometimes you will find a concert or choire, gymnastic presentations, and the community singing the national anthem. All fun stuff to watch.
I'm told the best celebration takes place at the Rhine falls near Schaffhausen. Fireworks, beautiful lights and lots of people are part of this fun. I've been to Rhine falls a few times but never on August 1st.
The photo pictured is from my friend Tony. He's done a great job of capturing the flags in the cobble stone streets of Zurich.