The longest day of the year and every street corner in France becomes a stage. Started in Paris in 1982, Fête de la Musique is now copied in 120 countries — but nowhere does it like the original. From classical quartets in church courtyards to techno DJs in Oberkampf, jazz in Saint-Germain, reggae in Belleville, and everything in between. It's completely free, entirely spontaneous-feeling (though heavily organized), and runs until sunrise. The vibe is joyful and surprisingly unpretentious — world-class musicians playing for nobody and everybody simultaneously. This is one of the best nights of the year to be in Paris.
The 11th and 20th arrondissements have the best street party energy. Avoid the over-organized corporate stages near the Palais Royal — wander instead.