The Dutch national holiday is the best street party in Europe. Amsterdam turns entirely orange — the national color — and the canals fill with boats carrying DJs, brass bands, and thousands of revellers. The entire city becomes a free market (the vrijmarkt) where anyone can sell anything on the street. Children sell old toys; adults sell vinyl and vintage. Simultaneously, every park has live music, every bar spills outside, and the canal boats are so dense you can nearly walk across them. It's chaotic, warm, genuinely inclusive, and completely unique to the Netherlands.
The Jordaan neighbourhood has the best street atmosphere. Arrive the evening before (King's Night) for the warmup parties. The canal boats fill up fast — book a spot on one if you can.